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.