A simple treasure table system

Here's a classic problem: The characters find some treasure – let's say there are diadems, gilt-framed paintings, jade figurines, and various other art objects. The GM describes them so that the players can write them down. The objects may not be sold for many sessions, before which many other treasures will be acquired from various sources, including different modules and the GM's improvisation.

The characters shouldn't generally know how much the art objects are worth when they find them. That should be GM-facing information. On the other hand, the GM shouldn't have to remember where every item came from, or transcribe each one and then try to hunt for it on the big list when the characters eventually try to sell it.

The typical solution is usually to bite the bullet: give out sale values along with treasure, or make it a hassle for the GM. Or perhaps compromise by giving out an indication of a treasure's worth and then rolling randomly based on the indication at the time it is appraised or sold.

 

A better solution:

I'm proposing a system which I've never seen in a TTRPG before, but it's so obvious that I bet I'm reinventing the wheel. It's similar to how item values work in the video game Dwarf Fortress.

We express each treasure as a phrase containing {class, descriptors}, where class is a type of item with a baseline monetary value, and descriptors are adjectives with multiplicative value modifiers. These are on big lists that are privileged GM information.

So the GM has a list of item classes coupled with base values that looks something like

Amulet   2 gold

Beads    1 silver

Cutlery  5 silver

Diadem   20 gold

Ewer     12 gold

Figurine 4 gold 

...

Then there's a list of descriptors, or possibly separate lists of positive and negative descriptors, each with a fractional modifier. Perhaps

Antique     ×5

Cracked     ×3/4

Gold        ×12

Half-rotten ×1/4

Jade        ×2

Large       ×3 

Rusty       ×9/10

Shattered   ×1/20

...

The GM has these lists at their fingertips. They are lookup tables, but of course if you did have a nice number like 20 or 66 or 100 entries, they could pull double duty as dice tables for treasure generation.

Illustration by Zed Nope

 

How do we use the tables?

A zillion sessions ago, the GM let the players know that they found an antique gold diadem and a large cracked jade figurine.

Perhaps they were described more fully (what does the figurine depict?) originally, but the GM made sure to communicate which were the key words, so that's what the players wrote down. The players weren't told the value, just the description.

Now time has come to sell these art objects. The GM doesn't need to remember anything about the treasure – where in the world it was found; what published adventure it came from or whether it was rolled or improvised; what rough-and-ready valuation the characters were given by a passing tinker.

The GM only has to do a couple of table lookups.

Diadem: Base price of 20 gold pieces. Antique: ×5. Gold: ×12. Actual value: 1200 gp. 

Figurine: Base price of 4 gold pieces. Large: ×3. Cracked: ×3/4. Jade: ×2. Actual value: 18 gp.

And that's all you need. The lookups are trivially easy; they're in alphabetical order and should fit on one piece of paper. The maths ain't hard.

 

Joseph Gandy (1771-1843)

 

The benefits:

There are seriously so many.

1. Hidden information stays hidden.

Players don't get information on value which should be secret. If they've found something made of 'ebonshell' and they've heard in passing that ebonshell is valuable, the word is a descriptor on the table and the players won't find out if that means "buy another round" or "buy a castle" until they seek out a valuation in-world.

Prior valuations stay consistent, too. If the GM allows a skill check for valuation, they can look up the true value, give an approximation (or a false answer if the check fails), and then completely forget they've given out that information whether or not the players go on to sell the item.

2. Descriptions correlate nicely with values.

Assuming you have a good set of tables, you're buying extra verisimilitude. The "cloudy garnet ring" you find in one dungeon and the "dull garnet necklace" you find two dungeons later have similar values, both are vastly less valuable than the "hundred-faceted ruby amulet", and that's exactly what players will expect.

Things that would otherwise 'just' be flavour start to matter more to the players. We can only take so much stuff back with us. Is the one-of-a-kind altarpiece cracked or just chipped? What's our best guess about how that compares to this sack of obsolete silver coins? Speaking of which,

3. There are learning opportunities.

We're all big fans of rewarding player skill, right? With this system, attentive players can begin to infer what words matter most for treasure values. This reflects the learning their characters would be doing.

On the other hand, the tables are

4. Easily reset.

If you want to start fresh in a new universe, or with new characters, or change GMs, it's trivially easy to just cross out a bunch of values for base items and modifiers and write in slightly different ones.

Players no longer know what to expect but the whole thing stays internally consistent, because you only tweaked the values. For the same reason, it's

5. Easily customisable.

Let's say you decided in this world, jade has mystic properties which make it worth more than gold. Cool, change ×2 to ×15 in the table and you're done. Any treasure you've already put out there is immediately converted.

If you're using treasure from a publication, when you go to convert an item you'll notice that it's described as "jade", check "jade" in the table, be reminded of your modification, and decide whether this particular thing is massively more valuable or whether you'll keep the value and change the material.

It's easy, because in general, this whole system is

6. Compatible with published treasures.

It's not much effort to start with treasures described by value and work backwards to create the descriptive {class, descriptors} phrase.

Suppose an adventure says "the bag contains three opals worth 300 gp each". What does that convert to? Well, you start by finding the "opal" class base value (or maybe "gemstone" is a class and "opal" is a descriptor), then flick around looking for more descriptors that will get you to 300 gp.

Maybe huge + dazzling + round + opal = 300 gp? Perfect. You've acquired more information about what the treasure is actually like. Or maybe it doesn't fit that they're "huge" so you try a few other descriptors and find that small + flawless + fashionable + opal = 320 gp? Close enough.

7. Simple calculations.

It's easy to price something up. We can put both decimals and fractions in the tables, so that people who are less proficient at mental maths can use a calculator. It wouldn't be hard to make a spreadsheet or online tool that calculates values very quickly.

8. Adaptive.

This single framework should work for most systems and settings. Only the tables will need to change.

Once published, individual GMs could hack further as they pleased. Have as many or few base object classes and modifiers as you want. It's easy to simplify or expand, because

9. You can hang stuff off the system. 

Let's say a character comes from a clothier background, and makes alterations to a "silk sash". Now it's a "tailored silk sash" and its value changes accordingly. A fighter is able to repair the "ragged rusted mail hauberk" enough that she can wear it, and now it's a "patched mail hauberk".

Want to get more out of jewellery and gemstones? Have a subsystem for inset jewels, which might add to or multiply an item's value.

Want to get into meticulous detail regarding some setting-specific fine arts? Add a whole extra table of modifiers referring to specific artists and times and trends and students and suspected forgeries.

Want collectors to be interested in specific things? Express that as custom modifiers. The antiquarian pays ×7 instead of ×5 for the "antique" descriptor. The archivist ignores penalties from the keywords "old" or "repaired" on books. The vizier only wants jewellery in good condition, so will pay double for any items without any negative modifiers, half otherwise.

Have item valuation and haggling skill systems? This framework just establishes the ground truth / base price, so those should sit neatly on top without you having to lift a finger.

10. No tracking.

It really bears repeating that the GM doesn't need to track any extra information, or resort to improvisation when they can't find the item they gave out months ago.

Wilhelm von Kaulbach (1805-1874)

So there's my idea! Do something cool with it. I've added "make a whole little book for this stuff and possible extensions" to the ideas pile.

Complications! Serendipity! Action resolution twists

An envelope gets tugged out of your hand by the wind. You kick your desk and slosh coffee everywhere. You bump into a friend in an unexpected place. A bird lands on your shoulder. The pen runs out of ink when you try to sign.

Because of how our own world works, we expect fictional worlds to be full of lots of little chance things which individually happen rarely. Pieces of serendipity. Unwanted side effects. Unexpected interruptions. Unforeseen complications.

Characters in the fictive world of a tabletop game should expect to encounter little surprises here and there. Not all the time; perhaps not as much as they do in the real world, because of the focus on exciting impactful play — but enough for verisimilitude.

Twisting outcomes ad hoc

TTRPGs often have rules for very consequential rare outcomes (critical hits, spell mishaps, fumbles, etc). But (especially in rules-light games) it is often down to the referee to come up with any smaller "twists": the complications and bits of serendipity we expect to happen not-too-infrequently when someone attempts to do something.

There are two problems with having the referee add twists to action outcomes on the spur of the moment.

1. The imagination is a resource. Thinking requires time and effort, a referee has a lot of mental overhead, and adding twists to action resolution begins with remembering to actually do it. Even an experienced and confident ref likes to have tools at their disposal to reduce mental effort.
2. If it's not a formal procedure, it can feel arbitrary. If the referee just tells a player "your sword hilt catches in the reins of the knight's horse as it gallops past and is ripped away, pinwheeling across the battlefield" it may feel unfair, even punishing. Why them? Why now? Why misfortune instead of fortune? This naturally leads to the ref only adding complications in low-risk environments, which is less interesting.

So here's an approach you can bolt on to any game to add more twists.

 

A procedure for twists

I was reading some older blog posts about (1) spark tables (Bastionland), (2) GM intrusions in Numenera (Alexandrian), and (3) the habit of rolling for complications (Necropraxis), and they got me thinking. We can put together some simple tools for adding twists.

The design goal is to create a procedure that is

• quick, simple, and useful to a referee,
• neither too game-specific nor too vague,
• open-ended and flexible. 

We just need a few dice tables and a basic rule for rolling on them. 

Here's the simple procedure I came up with:

1️⃣ The referee (or designer) should decide on the mechanical trigger for adding a twist to an action outcome. This will be system-dependent, e.g., "when the margin of success or failure is 10 or more", or "when a 01-03 or 98-00 is rolled on percentage dice", or "when rolling with (dis)advantage", or "when anyone spends a luck point".

2️⃣ Ideally it's something that players and referee alike can notice, so that it gets remembered, and eventually comes to be expected.

3️⃣ Now if this trigger applies during action resolution, the referee rolls 1d10 twice and consults the following dice tables, picking whichever of the two outcomes is more plausible for the context. Reroll if absolutely necessary.

(If there's no appropriate trigger for your system, you might roll 1d12 before each action adjudication and give a positive twist on a 12 or a negative twist on a 1. Or if you want lots of serendipity/misfortune and fewer dice rolls, just extend the following dice tables to 1d20 size and roll a pair of d20s for every action adjudication, one for a positive twist and one for a negative twist, ignoring results higher than 10.)

 

Dice table #1: Combat-specific twists

In a fight, one side's boon is the other's bane. The table entries refer to a "combatant" who should either be the character acting, or the opponent they are focusing on, as appropriate for the trigger. (This should work even for games without symmetrical combat mechanics, with a reasonable choice of trigger.)

1. Exposed. Combatant is drawn out of position, surrounded, or put on bad footing.
2. Toppled. Combatant is knocked down.
3. Lost grip. Combatant drops their weapon, gets it stuck in something, or loses their grip.
4. Disoriented. Combatant is blinded, dazed, scared, or demoralised by a combat event.
5. Jostled. Combatant is trampled, grabbed, or knocked aside.
6. Extra injury. Combatant suffers an additional incidental wound.
7. Ally harmed. Combatant accidentally causes harm to (or disrupts) one of their allies.
8. Armour broken. Combatant's shield or a piece of body armour breaks, is removed, or is rendered useless.
9. Weapon breaks. Combatant's weapon is made useless: a blade breaks, string snaps, gun jams, etc.
10. Impeded. Combatant is tangled or otherwise hampered by terrain or their own armour.

 

Next we'll look at random tables for general actions. We can't expect there to be a zero-sum symmetry like there is in combat, so we'll need separate misfortune and benefit tables. Choose the appropriate one for the trigger.

(Depending on the trigger, negative twists might still occur for successful actions and positive twists for failures. I think this is a good thing.)

Dice table #2: General action twists (misfortune)

1. Incidental damage. Whatever the character is working on or with (a rope, lock, computer, tool, weapon, etc) is damaged.
2. Extra time. The action takes longer than expected (the character may choose to abandon the task early when this becomes clear).
3. Costly. The action will take more resources than expected (the character may choose to abandon the task instead when this becomes clear).
4. Loud or unimpressive. A mistake or coincidence causes the action to get everyone's attention. This may be laughable, socially objectionable, distracting, or dangerous.
5. Minor injury. The character suffers some small harm in the course of attempting the action.
6. Crudely done. The action is performed clumsily or its effect is crude and sloppy, in a way likely to have later repercussions.
7. Unwanted side effect. Attempting the action also causes a problem, likely related to the method used and the circumstances.
8. Hidden step. Attempting the action reveals a new challenge which must be overcome before the action can actually be completed. *
9. One shot. Attempting the action reveals circumstances which mean the task can't be tried again following this attempt. *
10. Tougher than it seems. Attempting the action reveals something about the situation which makes the task harder than anticipated. Adjust it for others and for future attempts. *

* Note the last three entries may necessitate changing the details of the world. This approach might not work for everyone.

Dice table #3: General action twists (benefit) 

1. Skill increase. The character performing the action learns something along the way. This may be as diegetic or game-mechanical as you please.
2. Mastery. The character can do this specific action again (in this same context) without any chance of failure.
3. Positive side-effect. Performing the action also causes an unexpected helpful outcome.
4. Good return. The action takes fewer resources than expected to accomplish, and/or yields more of some measurable outcome than it normally would.
5. Quick. The action takes half the time it normally would.
6. Quiet. The action is accomplished stealthily and subtly, or there's a distraction elsewhere that takes attention away from it.
7. Impressive. The character performs the action in a way that's inspirational, smooth, culturally appropriate, or garners public approval.
8. Stacking. The way this action changes the world makes it easier for allies or harder for foes to accomplish some related thing(s). *
9. Discovery. The character performing the action finds something (information or an object) when they attempt it. *
10. Easier than it seems. Attempting the action reveals something that makes the task easier than anticipated. Adjust it for others and for future attempts. *

* Again, the last three entries may require changing the details of the world. You'll need alternatives if you don't like that.

The benefits of table-based twists

There are three main benefits to this approach.

1. SALIENCE. The simple procedure means easy referee decisions. It reminds the ref of various outcomes that should be possible. And it's a quick way of selecting between side effects.
2. PLAUSIBILITY. The tables are fairly general. Rolling twice and picking the more plausible twist is easier than having to think of a particularly suitable possibility, but is quick and flexible.
3. PERMISSIVENESS. When a game system doesn't overtly empower the referee to intervene in small ways, adding a defined procedure feels less arbitrary. The one I've written up is neutral with regard to the player characters; in games where characters are more skilled than their opponents, it may even be a small advantage.

You no longer need as many specific rules for monsters, traps, etc, because it all works inside the established fiction of the world. Now if a monster is described as having a hard shell, whenever "Weapon breaks" is one of the rolled options you'll instinctively pick that one without thinking too hard about it.

Alternatively, you can hang stuff off the procedure to extend it.

• A cursed sword might always favour the "Ally harmed" twist when rolled as an option, and doubles the effect when it happens.
• A sticky jelly monster always permits "Lost grip" as a third option to choose between, so that more and more swords end up stuck inside it.

The procedure can be completely player-facing if you want. In story-telling games you could even make the choice of twist a collaborative decision.

You could also use the twist procedure to simplify rules-heavy games, turning their specialised action outcomes into simple table entries and then discarding their complex action resolution mechanics.

Finally, you could build your own tables to come up with task-specific results. If your game is mainly about tracking, you probably want a tracking-specific table of twists.

A potential drawback: Combat asymmetry

This will give you different ratios of good and bad side-effects depending on the number of combatants involved. If a dozen characters fight one giant, or fifteen minions fight one player character, there's a risk of the solo combatant being buffeted by constant 'bad luck' due to the sheer number of rolls the other side is making.

Ultimately this comes down to choice of trigger. Some possible adjustments: Only accept the first two twists that get rolled each round (for combat systems with initiative). Only take the biggest margin of success from each side (for combat systems where everything happens at once). Identify one-vs-many situations and change the trigger to benefit the one. Give boss monsters the power to ignore the first negative twist they would suffer each round.

And of course you can codify rule zero. The referee should simply reject a twist if none of the possibilities rolled seem suitable for the situation. That way a mob of gnomes can't keep knocking the giant over, making her drop her club, etc.

Finally

I should note that this procedure is untested, but I hope to give it a go at the table in the future. I'd love to hear if you have thoughts or feedback. Leave a comment or let me know on Bluesky or Mastodon!

 

The art in this post is by Gordy Higgins. Used with permission.

'Reasons for reactions' to improve random encounters

You don't want your encounters, especially random encounters, to be susceptible to is-this-a-combat-or-do-we-ignore-it thinking.

Plenty has already been written about giving encounters extra contextual details (where are the creatures, what are they doing, what are they hiding, etc).

But it's also important to give the encountered characters the appearance of agency by varying their reactions. The orcs don't always attack on sight. The halflings don't always ask you to join them in a meal.

So how do they feel about you?

Different games go to different lengths with this.

🟩🟩✅ Varied reactions: The rules randomly modify how aggressively a particular set of encountered creatures react, in some way. Most games do this.

🟩✅✅ Default reactions: The rules specify a creature's or group's default reaction (friendly, suspicious, wary, indifferent, curious, issues challenges, hostile, fearful, neutral...), and modify this with a dice roll.

✅✅✅ Motivated reactions: The rules provide plausible reasons for encountered creatures deviating from the default reaction (in case the GM struggles to tie it all together).

That last approach, motivated reactions, is a very useful tool but few games do it. So here are some appropriate options you can roll or pick.

1d10 possible reasons the encounter is unusually friendly:

1. unusual individual/leader
2. need a favour
3. recently sated
4. intimidated and trying not to show it
   
5. hiding a secret
   
6. smell food on the party
7. recent festival, harvest, windfall, or celebration
   
8. hoping to steal / other deceit
9. feeling secure after recent victory
   
10. party is a reminder of old friend(s)
    

1d10 possible reasons the encounter is unusually hostile:

1. on high alert after recent attack
   
2. mistaken identity
3. resource-starved and desperate
4. rabid or maddened
5. hiding a secret
6. already in bad mood
   
7. subject to tyrannical orders
8. party inadvertently breaking taboo/custom
   
9. fear of reprisals from a greater threat
10. bandits, soldiers, hated nemeses sighted in area
    

"The minotaur is trying not to disturb a spider's web by moving, and settles for glaring at you balefully."

It's infamously difficult to get across motivations, secrets, and motivations at the table, so signal the reasons as clearly as you can to the players. Your encounters will have more verisimilitude, be more engaging, and be easier to improvise.

Random vs procedural generation for game content

Random generation and procedural generation (which is a little more than 'random generation with the crusts cut off') are powerful tools. As GMs and designers we use them to spark inspiration or to populate a game or setting with interesting content. But we use them, or ought to use them, in different ways.

Here's the difference, as I see it.

Random generation

Roll a dice, get an outcome. Or variants thereof.

Random generation is

👉 Extremely quick
👉 An opportunity to use big random tables, which everyone loves
👉 Useful for inspiration by hitting possibilities you wouldn't have thought of, even if you don't use the actual prescribed results 

But it may also result in content with major dissonances and peculiarities.

I think a little incongruence is good, but generating too much randomly can create a sort of silly homogeneity where everything is dissonant, nothing quite makes sense, and no world elements are linked or correlated except by accident. You get ooh-so-zany slop.

Over-reliance on randomness thus requires work to repair, which can itself be entertaining, but takes time and effort.

For example, suppose you roll a random encounter across multiple tables, and get: [roll] hundreds of ... [roll] skeletons ... dressed as ... [roll] jesters .... and they're [roll] hauling a cartload of ... [roll] scented soap ... through [roll] a desert in bloom.

It's something you wouldn't have thought of, sure. But it's too dissonant to be usable in most settings. You hear it and maybe an inkling of a consistent narrative jumps to mind, but the designer needs to plaster over the gaps, tweaking or adding things, to actually get there.

Zany. Too zany? Image by CDD20, via Pixabay.

Procedural generation

Technically a subtype of random generation, procedural generation uses a more complex function to go from inputs to results. It uses randomness, but has deliberate human design built in to create plausible outcomes.

This takes longer, both in the up-front design work and the use of it for creation.

Procedural generation...

👉 Both uses and creates interlinked/ordered/self-consistent information
👉 Combined human decisions and design with randomness to spark novelty but to constrain it in certain ways
👉 Results (ideally) in more plausible or verisimilitudinous outcomes

Examples include:

👉 Branching tables and subtables
👉 Little bits of pseudocode for dungeon room generation
👉 Features added to a consistent core, like a themed monster which gets appropriate thematic features generated via branching dice tables or if/thens

One Application

I'm currently working on a zine. Its premise is that wizards are powerful, crazed, unique, and have strange features which align with their individual theme. For me, that means procedural generation.

I'm exploring a process of taking a wiki article from, say, Wikipedia and pulling out a bunch of descriptive phrases. From these, you get semi-structured thematically-coherent content. Then you follow some guided rules to apply them to the underlying core, which is 'a creepy and erratic wizard'.

After enough customisation, you have generated yourself a wizard. The random element of procedural generation means your character has features you wouldn't have thought of yourself. The human-guided element means the wizard should be more plausible, or at least thematically consistent, than pure randomness generally achieves.

(More news on the zine as I progress with this idea!)

Improving Swarms for D&D 5e

As part of a creature project, I'm taking a look at improving the 'swarm of creatures' mechanics in Fifth Edition Dungeons & Dragons.

The problem is one of verisimilitude balanced against the quirks of the 5e combat system, and a desire to make swarms uniquely vulnerable to the things they should be vulnerable to while dangerous if you're fighting them without those things. Only fun solutions are allowed!

What are the essential characteristics of a swarm?

A swarm of creatures is a notable opponent because each of its diminutive components is, almost by definition, (a) mostly harmless and (b) trivially defeated. Only en mass are they dangerous and require effort to destroy.

Characteristic 1: Weapons shouldn't matter, but strategies might

A lot of TTRPGs massively undersell the killing power of a bladed weapon compared to a blunt strike in almost all situations. One exception is fighting a swarm.

Typical swarms are made from creatures so small that the more effective approach to fighting them would be to hit them with something broad, in order to crush as many as possible at a time. If you have six seconds to spend and you're fighting a homogenous area of a thousand flying bugs in the space in front and to the sides of you, then we can imagine shooting an arrow might kill ~0.5% of the swarm if you're lucky, swinging a razor-sharp blade could kill ~1%, and swinging an ordinary dining chair could kill ~5%. If they're ground-based creatures, stamping on them or rolling around on them are likely to be far better strategies than swinging a weapon.

So if a player character wants to fight a swarm, then we only have to consider whether they're in melee or shooting at range; to simplify we might generously allow melee weapons to be as effective as unarmed or improvised attacks, so that players don't feel silly just having their characters stamp up and down every turn. Ranged attacks should be much worse, though.

As the swarm's component creatures become larger and more dangerous, the martial skill and physical power of the person fighting them might begin to matter. But for heroic fantasy like D&D 5e, I think we would generalise 'fighting skill and power' to 'character level': CR 18 swarms should be made up of individual creatures of a kind that any 18th level character can destroy trivially and in quick succession in a fight; the same creatures might individually pose a small challenge to 1st level characters, but the 5e design parameter of bounded accuracy limits the degree to which this can be true.

Characteristic 2: Big, flowing, and diffuse

A swarm is made of tiny little freely-moving elements, and therefore behaves something like a fluid: it can get into small spaces, surround creatures, and so on. Healing, strengthening, or weakening an individual creature shouldn't have any impact on the swarm.

How large and dense is a swarm of animals? Dense enough to see it clearly, as a bare minimum. In practise, I think it would be more viscerally horrible if it's really dense, with creatures crawling all over each other.

• As a bare minimum density, I think we should imagine at least one flying bug in every 4×4×4 cm cube. Then we would have more than 15,500 bugs in a cubic metre, which is about the space you could swing a chair through.
• Alternatively, we can imagine one larger flying creature like a small bird or bat in each 25×25×25 cm cube. There would be 64 such creatures in a cubic metre.
• For a dense mass of beetles crawling over each other on the ground, we need at least one beetle every 2×2 cm. Then we would have at least 2500 bugs in a square metre.
• Likewise, for rats or tarantulas or other larger creatures, I would expect at least one animal every 10×10 cm, for at least a hundred critters in a square metre.

I envisage swarms as having a big dangerous centre part and a much less dense 'periphery' of creatures that continually enter and leave the centre, but are mostly harmless. We can think of the swarm as being all the creature in it, but it's mostly the ones in the core attacking and grouped up in ways that makes it possible to kill them at any reasonable rate.

When I sit back and imagine a swarm, the whole thing must be at least five square metres on the ground, or at least ten cubic metres if flying – preferably much larger. Anything smaller seems pitifully small. Of that, the dangerous core is maybe a fifth to a half of its area (or volume).

This back-of-the-napkin maths implies you're fighting ~150,000 wasps or ~640 bats or ~12,500 centipedes or ~500 rats.

It's a good place for a reality check. Here on Earth...

• A bat colony has several hundred bats
• A honeybee swarm has 5,000 to 40,000 bees
• A murmuration of starlings has 5,000 to 50,000 birds
• Army ants form swarms or columns of between 200,000 and 20 million ants
• A desert locust swarm is pretty diffuse, with 'only' 50 to 70 locusts per square metre but covering hundreds of square kilometres in total

Real-world swarms are probably much less dense than the ravenous fantasy swarms we imagine. But whether they are or aren't, the numbers don't seem off by multiple orders of magnitude.

Characteristic 3: Time required for attrition

Assuming a swarm is only dangerous because it is a very large group of marginally dangerous creatures, it should take a long time to destroy in melee combat.

If you have a six-second turn, maybe you can completely destroy half a cubic metre of flying creatures by swinging a chair through them, or annihilate a quarter of a square metre of ground-based creatures by jumping up and down on them. I actually think that's generous even for characters in a heroic fantasy genre.

Then with the parameters we've established it should take a minimum of 20 character turns to kill a swarm in melee (as a level-appropriate moderate challenge, 5 rounds for a party of four characters). For the kind of bigger, more dense swarms that we'd prefer, it 'should' take much longer to destroy a swarm without something that takes out a huge chunk out of it at once (see Characteristic 8, below).

Characteristic 4: Easy to hit

It shouldn't really be possible to try to harm a swarm and fail.

It doesn't matter if you're swinging an axe at bats or stamping on centipedes, we're talking about a packed area of low-intelligence creatures with little situational awareness, a flocking instinct, possibly driven into a frenzy, and surrounding their enemies on all sides. They're not getting out of the way.

In D&D terms, it shouldn't require an attack roll to take a swing at a swarm, and they should at least have disadvantage on most saving throws.

Characteristic 5: Dangerous in numbers

A swarm should be able to attack almost indiscriminately. Ideally, anything inside it should get hit; we might limit this to a 'multiattack' to make it faster.

As a swarm gets smaller, the amount of harm it can do should fall.

• If a swarm takes up less volume as it suffers attrition, keeping the same density, then the number of targets it can attack simultaneously goes down.
• If a swarm takes up the same volume as it is attrited, its density falling instead, then the amount of harm it does to each target goes down.
• If a swarm's volume and density are both reduced, then you could justify either option.

Characteristic 6: A reason for cohesion

The main reason (on Earth) that animals band together in swarm is to defend against predators. There's both 'safety in numbers' in the sense of an individual becoming statistically less likely to be predated, but also, the movements of the group can confuse or in some cases intimidate predators. There are rare exceptions, like army ants, which seem dangerous because they group up to hunt. I think it's safe to say that fantasy swarms are more like the latter.

A swarm sticks together, but clearly doesn't have to – its individual components aren't physically connected. It's a matter of taste as to whether parts that get separated can rejoin the swarm to continue acting in unison; I would rule that they can.

A swarm also can't react quickly or precisely or perform complex tasks, and its individual creatures attack pretty much blindly. In D&D terms, I wouldn't let it make attacks of opportunity: if you're in the swarm, you're being constantly bitten (with lots of miniscule harm adding up to HP worth of damage), and if you're not, you're not. If anything, a creature should suffer less harm for leaving the swarm's area sooner, but that's difficult to reconcile with D&D mechanics for only a small payoff.

Something is motivating the swarm to act as if it were a single creature. Maybe...

• A true hive-mind has emerged from the swarm, or
  
• A foreign overmind is controlling it, or
• There's some spell or fantastical natural force in play, or
• The individual creatures have a psychic bond

It seems likely that forcibly disrupting the swarm's cohesion would be particularly harmful to it. Depending on the nature of the outside motivator, the swarm might be particularly vulnerable to psychic damage, or it might shrug it off completely. I personally favour the former.

Things that affect a creature's physical body (conditions like paralysis, poison, and petrification) probably only affect one or a small number of bodies within the swarm, for negligible effect. We could model this as the minimum unit of harm in D&D, 1 hit point loss.

Characteristic 7: Extreme susceptibility to area damage

A little creatures which is individually below notice can be killed instantly by almost any attack. Some attacks are indiscriminate, hitting everything in an area. Even a really dense swarm probably has some room between creatures for such effects to penetrate.

It follows that effects like fire, force waves, toxic or corrosive clouds, rough weather, etc should do massive damage to a swarm. A swarm caught entirely within such an effect might struggle to survive at all! In D&D terms, it is not sufficient to model these kinds of things as different damage types. "6d6 poison damage to any creature in the cloud of poison" should kill a swarm; "6d6 poison damage to a creature hit by the arrow" should barely inconvenience it.

So does 5e capture these essential characteristics?

Not sufficiently, although the writers made an effort in that direction. Consider the six swarms in the D&D 5e System Reference Document (SRD).

Characteristic 1: Weapons shouldn't matter, but strategies might
Characteristic 7: Extreme susceptibility to area damage

✅ SRD swarms do resist the kind of damage usually associated with weapons.

❌ ...But on average a longbow will still do more damage than a club, which will still do more damage than fists and feet, i.e., the opposite of what we'd expect.

❌ More martially skilled characters deal substantially more damage than less martially skilled characters when smacking at a SRD swarm in their space. We wouldn't expect this, especially at low levels (where flailing around with something broad and heavy to crush dozens or hundreds will always be a good strategy).

✅ SRD swarms don't resist any of the classic area spell damage types, making damage spells a good choice against them.

❌ ...But nor do they resist single-target spell damage. And if an area spell does deal weapon-like damage, an SRD swarm takes half damage from it (which it really shouldn't).

Characteristic 2: Big, flowing, and diffuse

✅ The SRD absolutely nails the 'Swarm' trait. I don't think it needs to change at all.

❌ The SRD swarms are Medium in size. Even if we imagine this as the most dense centre part of the swarm, this still feels too small for any but the absolute weakest of swarms (admittedly all the SRD swarms have a low CR).

Characteristic 3: Time required for attrition
Characteristic 4: Easy to hit 

❌ The SRD swarms have similar HP to comparable SRD monsters, but their resistances effectively double it. However, their HP is unremarkable per the DMG monster creation rules, even factoring in resistances. They should be harder to destroy using single-target attacks.

❌ Likewise, their AC is typical for their Challenge Ratings, so a fair number of attacks (at least a third) will just miss them, even though that makes no sense.

Characteristic 5: Dangerous in numbers

✅ The SRD swarms lose half their damage output when reduced below half health, calling to mind 4e's Bloodied condition. I think only changing it one time at half HP is reasonable. It means a swarm's current number of component creatures is directly reflected in its damage, but doesn't create more mental load for the GM with a more complex way of doing that.

❌ To have a SRD swarm attack lots of creatures at once, the GM has to fake it by using multiple swarms together. Really a swarm should be larger and dangerous to anything inside it. Think about the verb form of the word 'swarm'.

Characteristic 6: A reason for cohesion

✅ SRD swarms are immune to most conditions, as we would expect. There are some edge cases like blinded, deafened, and poisoned which the designers let affect them (the first one possibly due to how light and obscuration are defined).

❌ Swarms probably shouldn't distinguish 'attacks of opportunity' from just continually attacking. Also, SRD swarms are affected normally by psychic damage despite being made up of hundreds or thousands of minds.

 

Evolution of solutions

When I initially wrote a more plausible 5e swarm based on that analysis, playtesting showed that I'd gone too far in the direction of realism. The fun was being lost.

Swarms could be blown up by quite low level spells, and a combat run strictly with melee attacks was a grind: arduous but not very dangerous.

In 5e, combats that go beyond three rounds are uncommon, ones that go beyond four rounds are rare, and so on. When the four PCs took six rounds to destroy just one of three lower-CR swarms I knew I'd miscalculated. Out of a sense of morbid curiosity, I gamed out eleven(!) more rounds before the fight was over.

Fortunately, I found some tweaks that solved this:

• Harmful area effects should do a lot of extra damage to a swarm (especially if all of it is in the area) without completely trivialising an encounter.
  
• A melee attacker can't waste every turn inflicting really trivial damage on a swarm. (It's fine to make single-target ranged attacks useless, because 5e has no strictly ranged glass cannons, and the character types that come near that all have access to area damage.)
• Swarms can have middling damage that drops when they hit half HP, as long as they deal some small damage on a miss, for an effect akin to a damaging aura.

With these changes, fights using just one or two spells last a good number of rounds. Multiple spellcasters willing to expend their best spell slot in their first turn can destroy swarms easily if they want to pay that cost. Fights with mostly mundane combat go longer than normal, but not outrageously so. More importantly, damage-on-miss makes swarms feel dangerous; between that and 'you can't fail to hit a swarm', the two sides are continually wearing each other down.

The final stat block isn't as completely verisimilitudinous as my initial vision, but overall it's a fun challenge to fight with a reward for thoughtful play, which is important. And the other changes to the SRD 'swarm' type monster implied by this article's analysis all worked well, so they'll be included in the final write-up.

Of course, to make this all hang together, the modified swarm needs a large number of traits (as well as some slightly unusual stat block entries like damage-on-miss and broad spectrum condition immunities). That's a no-no; it imposes substantial cognitive load on the GM, especially a GM trying to use it on the fly.

The next step, then, will be a challenge: Edit the text into a shorter form which presents the most important information in a way that's easy to find while keeping the writing crisp and clear. But isn't that always the case?

Put Flourishes, Fairy Tales, and Folk Beliefs in Your Fantasy World

Something fantasy world builders tend to do is

1. Take some interesting little aesthetic notion, often borrowed from a story, a history book, folklore, or a random generator;
2. Transform it into a fantasy element with thematically appropriate magical properties.

And that's great. But this is a call to sometimes not transform that little notion into actual 'functional' magic!

Earth's history is absolutely crammed full of little details, curiosities, artistic elements, superstitions, taboos, dead-end inventions, beliefs, art forms, and rumours that don't map onto anything impactful/real/important/true. Why wouldn't a fantasy world be similarly overflowing with these?

We live in the information age and people now still believe all sorts of completely preposterous things, not even as a matter of survival or entrenched cultural memory. In a classic pre-industrial fantasy world where the ground state is ignorance, people are going to deal with the great mysterious unknown around them by (a) trying to work out what works, and (b) just making stuff up. Both types of 'information' will be propagated. That's how people work, and the people in your fantasy world should feel like people.

Here's some suggestions.

Superstitions about dangers

Not every supposed way of keeping the monsters away actually does something. How boring would that be? Our world is full of superstitions meant to keep away monsters which don't even exist. That means you should add popular measures against goblins, vampires, spirits, ghouls, ogres, drakes, basilisks, and so on which simply do not work.

Remember: Nobody has enough information to know what's true and what's not. Even if the idea of confirmation bias has been invented in your world, the average uneducated person isn't going to have heard of it, and won't truck with it if they somehow have. Just like the average undereducated person in our world, and again – we're in an information age.

Superstitions about locales

Some places are sacred or taboo because of personal local history, not because of an innately magical nature.

You can have a big old battlefield without ghosts, and deep dangerous pits that aren't bottomless. The holy grove can just be regular holy rather than regularly dispensing miracles. If nobody goes to the place where the wicked Old Master was stoned to death, it doesn't have to be a portal to the realm of punishment, and the place where his sprawling manor was burned doesn't have to be a nightmarish megadungeon.

It's fine if some places work like this. But a world without unfounded local superstitions rings hollow.

Fairy tales, folk lore, and mythology

Here's a list of the world's fairy tales. There are many thousands of them and the list is incomplete. Like the vast majority of information from history, the most fairy tales never survived to pass into the written record. Note that none of these stories, as far as we can tell, are true.

The good news is that there's so many of them, you can just grab a few at random to fling into your own world and nobody's going to be familiar enough with the corpus to tell.

Folklore is deep and broad.

How about this rule of thumb: for every fairytale and mythological creature you put in your fantasy novel or game, add one that's not actually real in-world, just folklore being perpetuated. Fairies are real in the fantasy world, so people there believe in little fluttering proboscidate flingletons, which aren't. The inscrutable sphinx is real, so people believe in the twelve-metre-tall caustic tintosmaum, which isn't.

Religions, creation myths, and philosophy

Without making a claim in any particular direction, if you assume the world's major religious beliefs are incompatible with each other in terms of truth value, then a logical minimum of 5.4 billion people make a false set of beliefs central to their world view. And a possible maximum equal to the world's current population of 7.9 billion.

Now, I'll grant that (again, avoiding particular claims) our world doesn't have fantasy RPG clerics getting their daily allotted three or dozen or thirty verifiable magical miracles. But truth spreads slowly outside the information age. The existence in a fantasy setting of an extremely interventionist real pantheon (if you use that classic TTRPG trope) doesn't actually preclude local worship of a supposedly interventionist fake pantheon. Doubly so if it takes expertise to distinguish clerical magic from other kinds of magic.

It all depends on the nature of your cosmology, but personally I like when deities are standoffish or nonexistent, and weird new cults and religions pop up like mushrooms, and everybody thinks they're worshipping the real god(s) but there's no way, or no practical way, to be really sure. That rings true to me.

Either way, I suggest including some religious ceremonies that don't do anything (except make people feel good and forge stronger community bonds and so on). Religious rites don't have to have direct supernatural outcomes. You don't have to take the D&D route of turning blessings, ceremonies, funeral rites, holy water, holy symbols, etc, into spells and items with practical gameplay effects.

Pseudosciences and fake magics

Things like astrology and alchemy and the system of medieval humours needn't be in-game systems of magic or science. It's fine if you do want to play things that way, because these pseudosciences are flavourful and people have enough familiarity with them that they know what to expect (widespread modern misunderstandings of what 'alchemy' really meant notwithstanding). But if you do, you should definitely invent new pseudosciences for your fantasy people to get caught up in.

Again: People in our world, where magic doesn't exist, have believed in all sorts of magic, on the back of no evidence whatsoever. People in a world where they can occasionally see magic working should be more likely to have their minds open to such things.

That means that alongside pseudosciences, a fantasy world should have 'pseudomagics'. Piscomancy! Rust prevention magic! Soliferrous auras! Longevity rituals! Charms against moths! Whole new fields of supposed arcana! Is that local warlock a low-level magic-user, an ambitious dabbler with exactly one trick, a deliberate con artist, or completely deluded? It should be very difficult for a non-expert to tell.

Our actual history also has tons of objects that people placed significance in and ascribed powers to. Consider for example the 'Sator square' (an acrostic word square in Latin). It puts out fires. It eases childbirth. It cures toothaches. It's the basis for a love potion. It cures aquaphobia. It finds witches. Inscribe it on bread to cure rabies and insanity. Write it in pigeon blood to make a wish come true. Etch it into your fingernails to cure jaundice.

The Sator square obviously doesn't actually do any of those things. But people really believed it did. A fantasy world should have all sorts of things like this.

Terrain features

Our planet is home to lots of remarkable, awe-inspiring geography. In a low-technology world, real-world terrain can be a big challenge. Mountain passes can be extremely deadly because of the low rate of success of people tackling them, not because they're haunted by spirits or dimensionally scrunched or stalked by a gigapredator.

For every fantasy terrain element, include at least a couple of mundane ones.

Rumours

A healthy proportion of rumours should be completely spurious. But from a TTRPG gameplay perspective, don't go overboard. Make sure some rumours are very obviously false, as well as some more subtly false ones.

A neat effect for verisimilitude is to spin up false rumours based on things the player characters did or witnessed.

Flourishes, artworks, and personal styles

A neat little aesthetic detail doesn't have to be enhanced by fantasy (meta)physics.

A company of mercenaries march with a noose instead of a battle standard; it has no magical powers. The local villages have a specialist crop; it doesn't give you temporary hit points or make you levitate or drool blood, it's just funny-coloured pears. A distant monastery teaches a distinct style of martial arts that isn't supernaturally powerful. And some distant monasteries stick to beekeeping, illuminating manuscripts, and overeating.

We know of lots of little artistic embellishments, hoaxes, and weird experiments from pre-industrial history. The Voynich manuscript is a big one. People made sword blades with guns attached (and vice versa) as early as the 1500s. Sure, things like this can be the basis for unique powerful artefacts, but they don't have to be. Some of them should be prototypes that just don't work, or novel weapons that aren't actually as good as well-established ones, or an artist's cryptic drawings of a dream they had, or deliberate hoaxes. The strange, mysterious, whimsical, and exotic doesn't have to be translated into 'it's magic and has purpose X'. People on Earth have made all sorts of strange, mysterious, whimsical, and exotic things; all of them have been mundane, and they have been no less special for that.

Conclusion

To make a fantasy world feel real and lived-in, don't just fill it with fantasy. Remember to add little human-feeling elements from the real world, where pretty often a cigar is just a cigar.

Fantasy pseudo-anachronism part two: Aetheric boogaloo

Following up on yesterday's post, here are some thoughts on pseudo-anachronisms that didn't end up in the main article.

Additions

First, there were a couple of pseudo-anachronisms I had intended to mention. Nice beds with mattresses and pillows are major investments, certainly not something every person owned, even when they're just pallets made from straw sitting on the floor. (If you think a bed is expensive today, consider that it would have been a large fraction of a house's value in many pre-industrial places and times.) Also, inns for travelers to stay in. Inns were only common on major roads, pilgrim and trade routes, and in cities and market towns. The chances of a random village having an inn would be close to zero, even a village in the middle of civilisation. And even in a reputable inn, it would be a luxury to get your own private bed that you didn't have to share with a couple of strangers or traveling companions, let alone getting your own private room!

To have nice beds and pervasive inns in our fantasy world, we need a reason to have a culture of travel, in particular to non-notable destinations. We also need a cheaper way of making sleep furniture – maybe some ancient artefact has been churning beds out at a rate of fifty per day for thousands of years, or maybe there's a widespread plague of puffball pigeons (all feathers and no flesh), or maybe when a domesticated slime dies it dries up into something superficially like a beanbag chair.

Second, reader Lauren suggested the addition of "well-lit rooms after sunset". It's true! If you've tried to light a room with candles before, you've found that candle light is really very weak. Any kind of fire doesn't, uh, hold a candle to electric lighting. Lauren also pointed out that many modern people are used to the ambient light pollution of a big modern city; complete darkness is very disorienting. It's hard to keep your balance standing up in true darkness, let alone move around, but TTRPG rule penalties are often just a slap on the wrist. As with many things, inconvenient truths get handwaved away unless they provide excitement in the game.

I think well-lit rooms at night is particularly common in visual arts and film, where the viewer's ability to see most of the shot is pretty much the most important thing.

So 'convenient modern lighting' is a fantasy pseudo-anachronism. It's one that any number of fantastic technologies could solve (glowing magical crystals, cold-burning lanterns, the ubiquitous luminescent dungeon wall fungi, minor spells and charms, enchanted or holy candles, unusually bright domesticated fireflies, rushlights from the will'o'wisp marshes, whatever). Think carefully before making it a solved problem for the common person, though: clean, cheap, portable, bright light like we have at hand nowadays is a powerful technology. It takes terror away from the night and eclipses and deep dark caves. It drastically changes warfare. It changes sleep patterns and therefore labour patterns and local economies. It removes a constraint that can serve to drive gameplay.

Missing technologies

Rarely, fantasy takes things away from the generic 1300s-to-1600s technological milieu, rather than adding pseudo-anachronistic technologies.

For example, central heating, chewing gum, concrete, contraception, ice skates, and lighthouses were all invented thousands of years ago. I've seen a setting where characters in a snowy town had no way to cross a lake which froze every winter. And there's no excuse for not having a lighthouse guarding the dangerous shoals near a major wealthy port city. Some of the others aren't likely to come up, depending on what kind of ground the fantasy is going to cover.

Complex financial instruments, too, are fairly old (the word "credit" appeared in English in the 1520s, and at the time English-speaking states were economically a bit of a backwater; I don't know much about the history of banking but I would be surprised if continental Europe didn't have entrenched banking and other institutions in centuries prior, and the Islamic world and the East earlier still). I think sometimes TTRPG settings leave out promissory notes, banknotes, loans and interest payments, insurance policies, and so on due to a false perception that these are modern innovations.

The elephant in the room in this regard, of course, is gunpowder. Cannons were widespread in the West from the start of our supposed fantasy technological band, and early man-portable guns were in use well before plate armour reached its apogee. In China and its neighbours, gunpowder had been used for at least five hundred years prior to the period, initially as an incendiary weapon.

There are good reasons for not wanting gunpowder in a setting, reasons which have been discussed to bits. Everyone reaches a different answer to the question (some, possibly, because of misapprehensions imported from modernity about how powerful, fast, cheap, light, or accurate an early gun could be; I personally don't think preindustrial firearms being 'too good' is an adequate reason to exclude them from a fantasy setting). Gygax was notoriously against gunpowder in D&D, going so far as to say that the laws of physics in his fantasy universe were such that chemical reactions were weaker. I don't think that's a great solution, because it's both underspecific and implies weird knock-on effects.

If we want a world where 'black powder' gunpowder was just never invented, is that historically plausible? On the face of it, no. It's three ingredients, of which sulphur is very common in nature, charcoal is an incredibly important part of metalworking technology, and saltpeter can be refined from fairly common mineral deposits or bat guano. Additionally, 'classic' fantasy has early chemist analogues trying things out (I think modern fantasy has sadly transformed the word 'alchemist' to mostly mean 'magic potion-maker', rather than 'a philosopher obsessed with the idea of attaining physical, mental, and spiritual perfection via a mixture of study, experiment, religious ceremony, allegory, chemical means, mystery cults, etc').

But what that argument overlooks is that having access to magic might impede the development of gunpowder weaponry. Early experiments with explosive or incendiary mixtures probably wouldn't have been (a) taken as far, (b) seen as something remarkable, or (c) suggestive of exciting military applications, if two streets over from the workshop was an academy of war wizards suiting up for another day of hurling explosive fireballs, turning city walls to mud, and setting things on fire with their minds. Even assuming magical arts were at the time in their infancy rather than developed, they would have a competitive advantage due to their comparative versatility. So, inverted pseudo-anachronism: Solved.

(Conversely, if you wanted to take it in the other direction, and have gunpowder keep up with or surpass violent forms of magic, a world with fantasy materials might have better ingredients for a propellant. Materials that were more common, cheaper to make, easier to discover, safer to store, produced a more powerful reaction, burned smokelessly, negated the sound of their own explosion, or whatever.)

Pseudo-anachronistic systemic technologies

There were a few technologies I left out of the first article because they are more processes than inventions.

1. Classic fantasy has machines but no factory mass production.

There's an artificer, wright, engineer, or (sigh) 'alchemist' who makes devices. There's steam power, clockwork, waterwheel power, or complex systems of gravity power or compressed springs powering elaborate mechanical traps. There might be non-magical 'automata'. Sometimes it's almost a genre shift into steampunk or clockpunk. Sometimes it's subtle: the dungeon gates open and close with the right series of lever pulls and Detect Magic doesn't turn anything up, but further details about the mechanism aren't forthcoming.

Luckily for our settings, there are major societal factors necessary for factory mass production to flourish. It's not enough to have the idea and the metalworking skill. Labour must be at least moderately expensive (compared to thoroughly pre-industrial eras, not compared to today). There has to be the wealth and systemic control to acquire, move, and stockpile large quantities of raw resources. There must be pretty good ways to transport input and output goods. There must be at least a little hint of standardisation in the cultural zeitgeist. Things must be sufficiently peaceful and stable locally that the wealthy feel confident investing huge amounts of capital starting up a new kind of business whose nature is that it must be continually fed or suffer major costs. And it probably helps if there are enormous costly wars going on in the background to drive both demand and development.

Two thousand years ago, the Ancient Greeks had clockwork, a simple steam engine, and Heron of Alexandria described mechanical automata and a vending machine (a coin-operated mechanical holy water dispenser). But the conditions weren't right for industrialisation: It wasn't Steam Engine Time.

Still, if you want to play it safe, consider adding a rare, non-scaleable magical element to the setting's contraptions (some bit of fantasy metallurgy or alternative physics power source or unique irreplaceable artefact).

2. Classic fantasy implies advanced food production.

My impression of the typical TTRPG fantasy milieu is that even small settlements have great numbers of skilled workers outside the fields of food and textile production. Compare that to almost all preindustrial places and times, where the farmer-to-specialist ratio is somewhere between 90:10 and 99:1. The implication is advanced food production technology, but this is seldom directly shown.

There's two avenues to resolve this. You could say there's an enormous spiderweb of little farming hamlets and fishing villages, mostly ignored by the setting focus, diligently toiling to feed and clothe themselves and send their crop of food or textiles to market to pay their taxes (or send them directly to the tax collector, in less moneyed societies).

Or you could add the milieu-appropriate equivalent of spray pesticides, antibiotics, massive greenhouses, John Deere tractors, chemical fertilisers, advanced irrigation, and GMO crops. Let's say that stirge blood repels all insect larvae, and breaks down into a decent fantasy fertiliser. Water mages harness tiny elementals for drainage and irrigation. Weather witches work the weather. Migrating flocks of giant eagles regularly fix the soil nitrogen. The obsidian bullock pulls a plough slowly, but forever, night and day, without needing to eat or drink. A growthstone is costly, but all plants within two leagues of one grow at twice the rate, so you just have to keep up with the weeding. The peaceful living dead keep birds away for a while before degrading and nourishing the loam. And to cover gaps, the magic temple is happy to dispense endless miracle bread to the sufficiently needy.

3. In classic fantasy, big things don't decay.

Speaking of nourishing the loam... In the real world, everything is subject to entropy. Even stone degrades over time. There are startlingly close to zero stone buildings whose original roofs have stood the test of centuries. Earth settles, tunnels collapse. Most metals corrode. Wood rots or gets eaten, even in the dry. And – you know where I'm going with this – dungeons aren't usually well known for being dry. Ancient megastructures like lost castles and sprawling dungeons are sort of a fantasy anachronism, in that they are basically supernaturally well-preserved archaeological sites. In our world, furnishings and materials in them would be rotten within years, everything mechanical would have completely seized up within decades, the entrances (at a minimum) would get thoroughly sealed by a bunch of debris blowing in, and eventually the structure's integrity would fail.

This is of course no fun. Luckily there are plenty of possibilities. Lingering enchantments. Automata or invisible demons or extensions of the Gygaxian 'cleanup crew' which eat dust and grit and drifts of leaves. Magical materials that don't corrode or rot. Something to bear in mind is that most of these anti-entropy fantasy technologies are going to be valuable to people in the world, so by adding verisimilitude to your dungeons and ancient monuments you are also adding stuff that people are going to want to mine/harvest/tame/imitate and put in their own homes.

4. Classic fantasy makes outdated arms and armours contemporaneous with later ones.

Okay, this is mostly just a pet peeve, but it's close enough to the topic for me to justify cramming it in.

Particularly in the case of armour, your generic fantasy setting offers armours from radically different warfare/civilian contexts (almost always getting the armour itself wrong, but that's another story) as if any of them could be reasonable choices. In practice, people going into battle wore the best armour they could afford, perhaps modulated slightly by considerations of comfort. Let's look at mail vs plate, which is the biggest example (apart perhaps from 'leather armour' which is somehow both protective enough to sometimes be chosen over metal and quiet/fast to move around in; yeesh).

If a setting has the technology, expertise, and capital investment to make plate harness, then a fully protective suit of mail (hauberk including coif + aventail + chausses + gloves etc) is strictly worse than a suit of plate armour: the mail is either heavier or much thinner (because of ring overlap!), and more expensive (it takes more labour to make and rivet the large number of rings than to shape the smaller number of plates, and both are kinds of skilled labour!), and less protective (because mail flexes at points other than the joints!), and no less encumbering (assuming the plate armour is properly made, you can't do yoga in it, but that's about the limit of its limits).

The only advantages you could argue for mail are that it's slightly less hot to wear, due to its breathability (except, it tended to be worn over thicker clothing), and that it's easier to don and doff (definitely true: maybe twenty or thirty times faster, and you don't need assistance from a servant or colleague). Did both mail and plate exist at the same time? Sure; transitional armours increasingly covered the body with plate and retained mail at the tricky gaps (goussets, and then just voiders). Should a setting book place 'full plate' next to 'chain mail' and 'leather clothing armour' as options that just have different tradeoffs? No way.

Can we find a good rationale for having mail hauberks in the same setting as sophisticated high-coverage plate armour? Only, I think, at places and times when expertise in making armour plates is tightly controlled and/or slowly leaking out into the wider world. The only good reason to offer both these armours as reasonable options to player characters is if the massive difference in time to don/doff them is actually going to matter in play, and this must be the way the opportunity cost is framed instead of nonsense like 'plate costs more than mail' or 'plate is heavier than mail'.

This all applies to some extent to weaponry, too: fantasy TTRPGs love big lists of weapons from across many centuries, and some of them ought to be modeled as strict improvements of others. And to weapons platforms, like the chariot, which was thoroughly superseded by horseback riding, but still pops up in fantasy from time to time. Also the galley, which has three core assets (incredible maneuverability, naval ram, and capacity for beach landings) and three core drawbacks (high crew requirement, low cargo capacity, and relative fragility), but I've seen settings which included galley-like ships to evoke an Ancient feel while managing to ignore all of those factors.

Arms and armour are the products of a continuous technological competition – hence the term 'arms race' – and classic fantasy almost never includes what you would actually expect: weapons and armour (and tactics, troop formations, earthworks, etc) that are specifically designed for fighting giant enemies, invisible enemies, winged enemies, hordes of extremely small enemies, enemies that can't be cut or pierced, enemies that are slow but kill with a touch, and so on. Instead, at best, real-world weapons are used against them in novel ways. This is one of the few areas where fantasy actually needs to make more stuff up.

Pseudo-anachronistic societal features

Finally, I'm going to briefly go over a few things that aren't technologies. They're arguably pseudo-anachronistic, but are beyond the main scope of what I've been talking about with and frankly would need a whole series of articles to get into, and touch on topics which deserve a deep and sober treatment. For many of them I also think they could have become widespread features of societies earlier in our history, they just didn't happen to do so.

Actually, in an attempt to rein in my impulse to go on typing for hours, I'll switch to bullet points. These tropes show up in 'classic' fantasy quite often:

• General stores and grocery shops. Pretty modern idea.
• Lots of off-the-shelf products rather than things being custom-made, commissioned, or at least assembled on the spot. Historically, if you wanted to buy a knife, you'd likely visit a blade seller (who sells blades bought from a blade maker), and a hilt maker, and possibly even a separate knife maker to join them together if neither of the first two offered that service, and then you would go somewhere else to get a sheath made for it. If you were rich, you would possibly have any or all of those parts made to your preferences, and then might visit yet another craftsperson specialising in decorations (embellishing, engraving, insetting, etc).
• Civil police forces, or town guards who for some reason serve as constables. Not completely unheard of historically, but you're more likely to run into the local aristocrat's enforcers, or a town militia/guard with strictly military responsibilities, or just three people (a reeve, a coroner, and a magistrate) to be the law system for an entire shire, county, or small fief.
  
• Minor professions inexplicably organised into guilds; guilds that lack a religious/charitable structure; guilds operating like labour unions rather than corporations trying to suppress competition; guilds envisioned by people who learned the word from MMOs; guilds for major military technologies that really ought to be state-controlled... I could go on. I usually just shake my head and assume the word 'guild' is a spotty translation from the invented language the characters are speaking, not meant to bear any relation to the real world.
• The (correct, to be clear) modern perception held by almost all individuals and even by most states that war is bad.
• The notion that a war is likely to be for some abstract goal of 'power' or to extend a ruler's 'reach' rather than for territory and loot. In a world where land equals wealth, a successful war is a financial investment with a huge payoff (things like holy wars, wars of succession, etc, notwithstanding).
• People (correctly, to be clear) being viscerally and morally repulsed by what we now call war crimes and torture 'even' against 'the other side'. It's a depressing reflection of how groups of people operate that this is only a modern concept.
• Modern principles of individual liberty and rights, personal equality, and other individual rights. Anyone with basic knowledge of history knows that these were incredibly hard-earned and we are lucky to mostly now live in societies that have them at least in principle. It's not clear whether fantasy imports these because we're so immersed in them or because it's not fun to play without them.
  
• People living without major societal obligations and without a rigid societal, contractual, or familial relationship with the people ruling them. e.g., vassalage. I think fantasy settings tend to just pay lip service here, because it's not fun to have to bend the knee to your 'betters'.
• Conversely, in some settings, absolute tyranny existing unchallenged. Arguably more historically plausible, but even more plausible would be: the lieutenants and rich vassals think the rulers have far too much power + the rulers think they're giving up too much power and are trying to claw it back + there's a backdrop of masses of poor tenants and peasants desperately trying to get their established rights upheld. See e.g. the Magna Carta.
• (Pseudo-)democracies where everyone is franchised.
• Large numbers of empowered women with equal rights and with societal roles overlapping with those of men (or without distinct societal roles). Again, to be clear, a good thing, but rare historically. I have absolutely no expertise here but I usually see an explanation for how the systemic oppression of women came about that goes [average male physical strength advantage + power derives from strength-based violence + societies were more likely to succeed when the powerful set the rules + people tend to support existing rules (or, successful societies encourage supporting existing rules) → men seize and then hold and maintain power almost exclusively]. The good news is that you can excise this from a fantasy world by having magic more powerful than strength, or by reducing biological differences between the sexes, or by having interventionist gods who support equality, etc.
• More generally, no bigotry, slavery, or systemic prejudice. Sometimes this is because everyday common people are space aliens, by which I mean they aren't under-educated, clannish, selfish, fearful, violent, and ignorant of the wider world. Sometimes people are portrayed plausibly but intolerance magically doesn't happen at a wider scale. There are good and obvious reasons not to want bigotry in your setting or to confront it in your games, but (and now this list is just making me sad) pervasive intolerance has historical verisimilitude. Yeesh. How about we say that the fantasy world's populations are massively cosmopolitan, driven by ancient diasporas of hundreds or preferably thousands of peoples; everyone looks different to each other, even very locally, and innumerable culture are constantly blending. Or maybe we resort to magical divine intervention again to fix things.
• Speaking of which, there's the trope of 'everyone's religious beliefs are strictly compatible'. In a classic TTRPG fantasy, the gods definitely exist, everyone agrees on what they're like, everyone mostly agrees on their names, most people worship a single god even though there's a pantheon, and nobody is erroneously worshipping a god who doesn't provably (or provably doesn't) exist. This has always been quite funny to me. Maybe I'll write an article about interesting alternatives.
• Immortality as a desideratum only of evildoers (e.g., liches and sorcerer-kings). Likely imported from major modern religions; I don't think many nonreligious people are keen to grow old and die. The trope is kind of compatible with there provably being a good afterlife, but that's not always the case in a fantasy world, especially when you're not one of the tiny number of people with a divine magic pipeline.
  

There we go. If you think I missed any notable pseudo-anachronism, leave a comment!