I wanted a cohesive system for building arbitrary fantasy worlds.  While cool games exist to solve this problem, I wanted to make something for myself to build on over a few months.

I come at problems from the dark underbelly of systems theory instead of straight forward paths.  To grow a bean, first I must create the universe.  I started on core research, read papers and books, and started building a core model.  Except, these models I worked from base themselves in the actual world.  Fantasy worlds have one component they lack: magic.

Being handy with a notepad, I scratched out a generic descriptive model for magic systems I found I liked and worked with other cultural systems  – economics, geography, state, military, religion. It had tunable knobs without needing math or specific RPG systems or to open a book on urban planning.

In this post, I offer a generic method for modeling fantasy magic from a societal and cultural perspective that you can bolt on to any world-building exercise.  This isn’t a game system per se, and it is not for any specific, popular RPG system. If you wish to use this, you can plug in the engine from your favorite RPG and use these abstractions in your model.

This model also works to simulate science in a non-scientific culture or high  in a low technology culture.  Remember Arthur C Clarke’s Third Law.

Any sufficiently advanced technology is indistinguishable from magic.

What is a Model?

What the heck is a model?  Encyclopedia Brittanica gives this as the definition of a scientific model:

Scientific modeling, the generation of a physical, conceptual, or mathematical representation of a real phenomenon that is difficult to observe directly. Scientific models are used to explain and predict the behaviour of real objects or systems and are used in a variety of scientific disciplines, ranging from physics and chemistry to ecology and the Earth sciences. Although modeling is a central component of modern science, scientific models at best are approximations of the objects and systems that they represent—they are not exact replicas.

You can think of an RPG, any interactive constructed world including an online world, or a fictional world as a simulation model describing a theoretical world and the rules that govern that world.  Good or bad — that depends on how well we build up the model and what fidelity.  Sometimes we don’t need that much fidelity.  Broad strokes are fine.  The long sets of sourcebooks and expansions on my shelf are a testament that we like fidelity, though.

In game design parlance, we build up models using established systems. Those systems have agreed-upon internal mechanics with boundaries and failure conditions — i.e., we roll a d20 in D&D5th Ed to model an action like swinging an axe or a bit of parkour.  We tune those worlds so that they’re not wildly out of balance and don’t drop into uncanny valleys. We want our model to work and not allow a die roll to knock the whole thing out of whack.

We have some popular models:

  • Want a modeled world inspired by Tolkein’s Middle Earth but with hella more stuff?  Play D&D5th Ed.
  • Want to tinker with and inhabit a model of a decaying world taken over by cool criminal gangs?  Play Blades in the Dark.
  • Want to model a world where secret government societies hunt down and destroy horrible hidden vampire societies? Play Night’s Black Agents.

What is a Good Model for Magic?

Almost all RPGs have a system to simulate magic in their constructed world.  Magic, it turns out, is so thematically potent in RPGs — much more so than a system of economics or a system of government — that magic with unclear aims tends to muddle the setting.  Magic with active aims with clear thematic roles brings the entire setting up to a higher level. The trick is to keep magic both thematic and balanced so that it doesn’t overpower the world but also act in concert with the rest of the game’s internal themes.

This model for magic doesn’t provide tools to scale magic up or down from a pure systems simulation perspective but helps to set it in context so that it functions thematically and is internally consistent with the rest of the worldbuilding exercise.  It also informs the rest of the world.

Triangle of Magic

A majority of magic systems (not all, but most) can be assessed on three aspects (variables): UbiquityImpact, and Cost.

  • Ubiquity Is a measurement of how rare magic is in the model and how aware common people are that magic exists.  If magic powers the airships that glide overhead or the steam engines that power the 12:40 pm train, magic is ubiquitous.  If magic only manifests in the minds of mad thinkers who pray to dark Gods while dwelling in farmhouses on the shores of 1920s Maine seaside farmhouses, then magic is not ubiquitous.   The underlying aspects to ubiquity are usability and social acceptance.
  • Impact is a measurement of both the impact of magic’s existence on the overall world.  A magic spell that can destroy the world or a galaxy or the universe has an immense impact.  Magic that works on a personal level has a small impact on the world.  It may be potent, but the impact is small.  The underlying aspects here are effect and magnitude.
  • Cost is the measurement of the cost of using magic on the environment.  Sometimes magic is virtually free — or magic costs 100gp pearls.  Alternatively, magic costs sanity, sacrifice, or huge piles of natural resources harvested from the ground.  The underlying aspects are resources and humanity.

We can assign to each of these attributes an intensity of 0-100 with 0 as a minimum and 100 as a maximum. This is a standard triangle graph:

The triangle has a forcing function to enforce a balancing effect on the world.  Big cost — big impact.  Ubiquitous, cheap, common, and weak.  Balance between forcing a costing function and an impact and how many people have access.  Hanging in the middle is all three aspects at work.

Let’s look at a quick and simple example.  In the world of Avatar: The Last Airbender, magicians practice magic through bending via martial arts stances.  Magic is highly ubiquitous: even if only a percentage of the population are benders, everyone knows it exists, and magic users are everywhere.  Unless you’re the Avatar or Fire Lord Ozai during a flaming comet, the impact is mainly local and personal — flying, healing, throwing rocks.  The cost is non-existent.  There’s some handwaving at the cost, but benders never seem to run out of bending unless they exhaust themselves from their martial arts moves.

Expanding the Triangle — Extracting Further Aspects

We can solicit much more detail out of our model by defining sub-aspects within ubiquityimpact, and cost.

Aspects of Ubiquity

Ubiquity is how common magic is in society.  Beneath ubiquity, we have acceptance and usability.

Usability: How easy is magic to learn, wield, and use for a common, everyday person?  Is magic a simple tool, or does it require an elaborate ritual, gear, or tooling?  Can magic only be wielded through a special bloodline or class?  Alternatively, Is it like electricity and magic runs through everything?

  • Literacy: Can the magically proficient transmit information about the instruction and performance of magic through the written word, so anyone without the writer’s direct instruction learn, understand, and practice it at any random later date in time?
  • Education: Does the practice of magic require special schooling, apprenticeships, and tutoring?  Is the use of magic innate, and wielders can use it from birth?

Acceptance:  How accepted is magic by society? Is magic a dark secret, or is it persecuted by the Church? Is magic forbidden by law? The Gods?  Is it like electricity, so accepted it’s part of the furniture?  It is possible for Social/Legal/Religious acceptance not to be in harmony.  The Church may disapprove and excommunicate you out if you cast magic, but the state won’t punish you for usage.  Alternatively, the people see magic as an underground resistance to an oppressive state.

  • Social Acceptance: Does society at large accept the use of magic?  Do the common people applaud its use or at least ignore or accept it or find it helpful?
  • Legal Acceptance: Are there state consequences for the use of magic?  Does the state have public or secret laws governing the use, pursuit, and punishment of magic in society?  Does the state see it as part of the fabric of broader state power?
  • Religious/God Acceptance: Does the Church approve of the use of magic?  Do they have their own magicians? Is magic expressly and clearly forbidden with the Church’s own laws and systems for meting out punishment?  This also covers the personal opinion of an actual God should one be involved.  If a God doesn’t care for magic, or is pursuing an enemy God’s magic, or using magic for the state, then the God has an opinion.

Features of Impact

Impact is the physical and psychological effects magic use extracts on society and the ecology around the society.

  • Effect: Effect is what it says on the tin.  Does casting magic cause a positive effect? Neutral? Is it like engineering and science where the effect is to build tooling for humans? Is it all geared toward infinite bunnies (bad) or releasing Nyarlathotep (equally bad)?  What does the magic do on people and the world around it?
  • Magnitude: What is the maximum cast radius for a spell?  Most magic is localized, but maybe it levels mountains, calls down the rain in a drought or swallows up entire cities.  Is magic small or big?

Features of Cost

Cost is simply that: what does it cost a person, a society, and a state to use this magic?

  • Resource Utilization: What resources does casting magic consume?  Are these cheap resources or expensive?  Plastic straws or human souls? For example, most D&D5th Ed is extremely cheap cost with some notable exceptions but calling down Quetzalcoatl through human sacrifice is expensive in people and after-ritual cleaning costs.  High resource utilization magic leads to resource exhaustion (and magic exhaustion).  This is a convenient hook into state and military considerations.
  • Humanity: Does magic consume sanity?  The caster’s body?  The caster’s very soul?  All of these are limited resources.  This means the caster, and magic, have a limited time supply until reaching resource exhaustion.

That’s it.  Figuring out where a magic system sits on the triangle and then exploding out the various variables underneath the three main factors and applying some constraints generates a decent model.


Let’s pass a few well-known systems from fiction into this model and see what kicks out.  These aren’t RPG per se, but they’ve been converted into variations of them.  I chose these examples for their general familiarity and for their breadth. They’re useful expressions of random fictional magic systems with analogs in games. Each is different in tone.

I have also mocked up:

  • Call of Cthulhu
  • Shadowrun
  • Mage: the Ascension
  • Blades in the Dark

After examples, let’s build two of our own.

Example #1: Forbidden Realms

Extremely high ubiquity, low to gargantuan impact, moderate cost

D&D.  It’s a great version of an aggressively magic-rich environment.

A world where portals to the Elemental Planes open on street corners, scrolls hang around in dingy boxes in dungeons, and even the thieves can cast a good spell or two.  Magic schools are correspondence courses, sometimes people wake up in the morning with new magical powers, and  Tiefling Sorcerers order visit from the best restaurants.  Magic isn’t just ubiquitous.  It’s a required survival skill to get down to the corner store.  The state loves magic.  The Church is into it.

Earlier versions of the game had magic slightly less ubiquitous.  Now all the classes have some sort of magic.  We can assume magic starts in kindergarten and works up from there.

As for impact — it depends!  A vast majority of introductory available spells are localized effects or single point to point spells.  Then we get into the 5th level of spells and there’s cloudkill and delayed blast fireballs and it goes downhill from there.  On average most spell usages are things like identify and barkskin and healing spells.  At the high end of the bell curve, it’s blasty time.

And on to cost.  Honestly, costs for most spells simply aren’t that much out of the average adventurer budget.  A few extremely evil plot spells cost a bit of humanity here and there. Resurrection sure isn’t cheap.  For the most part, though, while casting isn’t free, it doesn’t break the bank either.

Cost becomes more interesting when we consider personal resource cost.  A mage can only cast X spells per day.  A sorcerer and a warlock have a limited list but easier access.  The other classes have an even more limited range than that.  Magic is more of a personal resource management game than a worldly one.  There’s choice, but there’s so much choice.

UsabilityCantrips and Level 1 spells are gateway spells.
LiteracyScrolls are everywhere: in stores, dungeons, storerooms, libraries.
EducationWizard schools are ubiquitous enough to kick out wizards who get eaten in dungeons.
AcceptanceNo overarching social repercussions while used in an acceptable manner.
SocialSociety generally doesn’t like magic used for evil.  Beyond that, cantrips for everyone.
LegalThe law assumes everyone has magic.  Laws more tuned to the effects (murder, theft, etc.) then magic use.
ReligiousEntire Gods and religions are dedicated to magic.
EffectTiny to enormous.
MagnitudeTiny to enormous.
ResourcesSurprising cheap!
HumanityAs long as you don’t become a lich, magic is light on the humanity.

Example #2: Harry Potter

Extremely high ubiquity, low impact, very low cost.

The world of Harry Potter is broken into two — the world of magic (magical) and the world of muggles (normies).  Even if only 10% of the population is capable of magic, and it sure seems that way, it’s still a vast world population who are either magic sensitive or magic aware.  Even if it’s only 0.01% of the world, that’s still 60 million magic users. That’s a viable secret online social network.

Everyone in the magical world is aware of magic and its everyday presence.

The magical world conforms to magic.  Spells are written in books and books are commonly available in libraries and bookstores.  Children are sent to (free, state-supported) schools where teachers perform instruction with clear goals and objectives to integrate wizards into society.  Also children, on an appointed day, receive wands to channel their magic — apparently for free. Society not only accepts magic but it is written into institutions of the state.  There is no comment whatsoever from the Church, should there be one.

One might even say that magic is the state in Harry Potter.  Most conflict in Harry Potter is not magical at all but political.

The magic in Harry Potter’s world, removing the magical beasts, is small stuff.  Magic opens doors, grows plants, scries mirrors.  Even big, adult-sized combat magic is all confusion spells and air shoves.  Very rarely someone casts a spell with much effort and cost to significant impact, but this is rare enough to make newspapers and appear in history books. In general, Harry Potter magic is utilitarian. Wizards drive (flying) cars and ride on magic trains and still need to work to earn a paycheck.

Harry Potter magic has no material cost on the world.  Occasional ritual spells use essential and rare components but, for the most part, it’s a word and a wave of a wand.

The Harry Potter world is familiar, utility, wide-spectrum, low-impact magic punctuated by the rare and notable big impact stuff.

UsabilityRequires innate talent. Once a wizard has his or her wand, magic requires pronunciation of a few syllables.
LiteracyBooks of magic fill bookstores and libraries.
EducationSystems of lower and higher education trains future wizards.
AcceptanceWithin the wizarding world, everyone casts magic.
SocialSocial repercussions are political.  Magic is politically neutral.
LegalLaw focuses on the more political ramifications of magic instead of magic itself.
ReligiousWorld has no comment on religion vs magic.
EffectSmall — opening doors, finding lost objects, flying cars.
MagnitudeSmall — personal level, localized casting.

Example #3: X-Men

Medium ubiquity, medium-to-high impact, low cost. Depends on the storyline and author.

In the X-Men, children born with the X-Gene evolve into mutants.  These are essentially superpowers (although Grant Morrison’s New X-Men run had some interesting takes on non-useful expressions of the X-Gene).  We assume that the X-Gene generates a superpower of some utility from Shadowcat and (sigh) Dazzler and everything in between and treat these superpowers as magic.

This magic is somewhat ubiquitous.  Common people know it exists.  It shows up in the news all the time.  The Brotherhood of Evil Mutants had their own country for a while.  However, governments frown on it and systems of laws exist to suppress and punish it. Normal people are generally racist toward mutants and treat them with open hostility.

Magic is generally also innate and requires no instruction (for the common case).  Either the X-Gene does a thing, or it doesn’t.  Can turn to diamond?  Great.  Focus and turn to diamond.

As magic is an expression of genetics, magic is passed down through bloodlines, making it exclusive.  This limits the ubiquity of magic.

The impact of magic runs from shifting through walls to literally blowing up suns.  If we look at the core X-Men (Iceman, Cyclops, Storm, Jean Gray, Wolverine, Beast, etc.) X-Men magic can tear up the place.  Storm alone is a high impact and high magnitude and high effect.  All she needs to do is summon a tornado.

The cost is meager.  Using X-Men powers doesn’t cost anything in material resources at all.  One might say it wears away at their humanity and they pay a cost in social acceptance, psychological stability, and long term happiness (see cost modifier).  On the other hand, they hang out at a massive mansion in Upstate New York with their friends all day, so it’s not all bad.

Interestingly, for various superhero variants, we can tweak the knobs a bit.  Superpowers can come at personal cost (eating away at humanity and vitality) only to be restored by some mystical foozle. We can make supers more demonized (less ubiquitous, rarer) by raising the cost of powers and having them pull vitality from bystanders and imposing a higher social cost.  Now we have a White Wolf game.

UsabilityEase varies wildly with expression of the X-Gene.  Requires X-Gene to wield.
LiteracyWhile training exists to help control the X-Gene, it expresses itself around puberty.
SocialPeople who are not mutants do not care for mutants.
LegalThe state persecutes mutants for mutations sake and built laws to criminalize the X-Gene.
ReligiousThe church is silent on the X-Gene.
EffectSmall to destroying worlds.
MagnitudePersonal localization to encompassing solar systems.
HumanityMutations are rough on the soul and sense of self.

Example #4: What We Do in the Shadows?

I love Taiki Waititi’s “What We Do in the Shadows?”  It’s far more Dracula than White Wolf.

Almost zero ubiquity, medium impact, big cost.

The main reason no one has come to stake the Vampires living in the house on Staten Island is that no one even knows they are there.  Ok, they’re supposed to take over the New World, but they don’t even have their block locked down yet.  Maybe next year?

Yes, in the world of “What We Do in the Shadows,” some vampires hang out, and they have the occasional party, and there’s a secret society or two. There’s maybe 0.1 Vampire/square mile of Vampire Inhabitance.  Vampirism really isn’t accepted by society at all, but there’s so few of them the state doesn’t craft specific Vampire laws. They prosecute and punish the cost vampirism extolls.  The Church is not a fan of creatures of darkness (see poor Nandor sitting in the Church during a funeral of one of his living descendants) but God just kind of cooks them, so that works out.

Power is innate.  Training takes about a day, maybe two, then off you go — no Vampire schools.

Impact dramatically varies based on Vampire age and some random factor of Vampireness.  Mostly, power is localized to the self — turning into a bat, flying, hypnotizing people, that sort of thing. It’s possible Vampire magic is much more potent than depicted at in the show — it’s hinted at — but our Vampires are lazy and hapless.  Except for the daywalking energy vampires — they’re ridiculously, almost stupidly, powerful.

The cost is high.  Not only does it cost the vampires their humanity, but they eat people regularly.  People are a pretty big resource, but if the vampires start depleting the local supply in no time, they’ll be no humans and many cops.

UsabilityEasy.  Think hard and become a bat! Requires blood transmission to become a vampire.
LiteracyVampires are obsessive about their own histories but do not transmit Vampire “secrets” in written form.
EducationLittle to none.  A small tutorial period and you’re good to go.
AcceptanceHumans do not care for the undead.
SocialWithin undead societies, things are great.  Among humans, things are not so great.
LegalThroughout history, the state has persecuted the undead because the undead eat people to power themselves.
ReligiousThe Church believes the undead are bad.  Vampires burn to ash when exposed to holiness or purity.
EffectVampire magic is pretty potent.  Living forever, flying, teleportation — all good stuff.
MagnitudeVampire magic is localized to the self and localized victims.
ResourcesThey eat people.
HumanityBeing a vampire is hard on the body and the soul.

Construction #1: Darkest Souls

RPG Summary: Dark gods from before time lie sleeping.  An ancient cult, more ancient than writing or cities, worships them and siphons godlike power for its own dark purposes.  The cult has burrowed into every corner of the state worldwide.  Every major historical event leads back to the cult.  Soon, they will wake the dark gods.  You will either destroy their agents or be co-opted.  (System – Gumshoe? FATE?  Action Priests with Guns.)

Ubiquity: Very low.

Only the cult and those who belong to the church agency who hunts the cult and extracts them know it exists.  Transmission about the cult is through ancient and near-modern documents found in arcane corners of the world.  The only way to learn actual magic is by caving in, joining the cult, and having magic beamed into one’s head via sleeping, horrible gods.  Revealing the existence of the cult will get you outed, excommunicated, framed for crimes you did not commit and turned over to the state.

Impact: Very high

The cult is potent.  They use magic stolen from their dark gods to deceive, lie, co-opt, control, and worm their way into the highest levels of money and power.  The effect is high, but the sheer magnitude of their reach is breathtaking.  Should they win and wake their dark gods, the world will fall into slavery.

Cost: High

The cult sacrifices the bodies of victims and when victims are scarce, their own bodies to cast spells.  Since the dark gods demand a human sacrifice to power true magic, the cult tends to operate in more lawless corners of the world where law enforcement won’t find them, and victims are plentiful.  If the cultists use themselves, eventually they’re used up, and they die, so their body is a carefully husbanded resource.  Operating out in the open is just a non-starter.

The cult’s magic is focused mainly on manipulation with a good dollop of shape-changing, infiltration, and any magic dealing with shadows.  You have the church, the internet, modern technology, and guns.  Lots of guns.

UsabilityUnless you’re a member of the cult or stole magic from the cult, highly difficult to wield.
LiteracySome information in Middle Eastern and Asian archeological fragments.
AcceptanceUnless you’re a member of the cult, you’re not a fan of the cult.
SocialMost people are unaware of the existence of dark gods.
LegalThe state considers magic a mortal threat and mobilizes against it.
ReligiousThe church considers magic a mortal threat and mobilizes against it.
EffectPretty powerful — mind wiping, shape-changing, infiltration, perhaps hacking technocracy magic.
ResourcesSacrifices animals, people, things, their own bodies, everything living.
HumanityConsumes the cult or anyone who stole magic from the cult from the inside out.

Construction #2: Wandering Cities

RPG Summary: Cities of pure magic float at cloud height miles in the air.  A thousand years ago, wizards discovered how to harness magic into grand engineering civil works. Along with damming the great rivers, shifting forests, and clearing deserts, the wizards lifted the cities from the trappings of geography and climate and allowed them to wander.  Since the Great Lifting, people have prospered. However, nothing in this world is free: the great magical engines powering the cities requires a continuous source of Xadril, a rare metal found under mountains.

More than one city floats in the clouds.  The reserves of Xadril are running out.  And, the ground dwellers, those Left Behind, have developed their own technology in the past thousand years.

Ubiquity: Pervasive

Look up and on a clear day, standing on the ground, you’ll spot a Floating City.  If you live in the Floating Cities, magic is everywhere.  It runs like electricity and powers an early 20th-century technological world of magic streetcars, magic phonographs, and magically lit city streets.  Not everyone in this world is a wizard, but magic is more like physics and engineering than the exclusive world of wizards and magical schools.  Wizard engineering is a standard part of the University curriculum.  Magic Engineering books are found in bookstores and libraries.  It’s a well-paid profession and a major tool of the state.

Impact: Huge

When cities are floating in the air, and magical engineering can terraform the world, magic has both a massive effect and a massive magnitude.  Magic is essentially the inner workings for civil engineering and electrical engineering.  Think Hoover Dam.

Cost: High

While magic has zero humanity cost and is 100% safe for humans to work, use and cast, strip-mining mountains for Xadril has a clear ecological cost to the planet. When it runs out, do the wizards turn their eyes to space?  Do they strip mine their solar system?  Do the cities go to war with each other over Xadril supplies?

UsabilityMagical engineering requires training but otherwise no barriers to use.  Requires Xadril.
LiteracyBooks found in libraries and bookstores.
EducationMagic Engineering Universities established and open to qualifying students.
AcceptanceMagic makes life much simpler for everyone.
SocialPeople use magic without thinking hard about it.
LegalLegal system accepts magic and promotes laws to enable the expansion of magic further and magic research.
ReligiousReligious systems accept magic.
EffectCan float a city!
MagnitudeCan float a city!
ResourcesRequires Xadril, a rare resource that is rapidly depleting.

Next Up…

Some extra time and cleverness could turn this blog post into a highly useful FATE-based toolkit for describing magic systems with Aspects.

This is a tool to start building up some bigger fantasy cities.  The next shot is likely to see how this magic model interacts with a governmental/state model and start building some moving parts.  Establish the full model that covers building cities and then, using the model, build a few cities and see how it works.