How to Write Believable Magic Systems in Fantasy

Let’s face it, most fantasy writers are in it for the magic. And I can’t blame them—it’s much more exciting than our mundane reality.

It’s what got me into writing fantasy in the first place; I’ve been to reality, and even though I haven’t lived through all possible human experiences, I think I get the gist. Fantasy, on the other hand, is a land of shiny, endless possibilities.

But while liberating (from office jobs and pesky laws of physics), fantasy writing presents a different kind of challenge: how to write magic systems that feel believable?

While most fantasy readers don’t expect (or want) to read a manual on how the ancient mystical crystal works on a sub-molecular level, or even know where the wise, ancient turtle got its wisdom, they do expect the magic system you use in your book to make sense and follow some internal rules.

A believable magic system usually has four core components:

1. It’s not your easy fix for complex situations

2. Its users have limitations

3. Using it requires training or tools

4. It has a source

Let’s dive in.

1. Magic shouldn't be a convenient plot fix

Remember how in LOTR the heroes barely made it out alive when suddenly, eagles? Those eagles are perhaps one of the most prominent pieces of criticism I’ve heard about The Lord of the Rings.

They arrive precisely at the right time to save the day, and it’s never explained why they didn’t show up at any other critical moment. It’s also unclear why, if they are always available and ready at Gandalf’s call, they didn’t rescue our heroes from the myriad of other life-threatening situations.

Magic often appears in stories much like the eagles in LOTR—used at just the right time to save the day (and the heroes). The problem with that is that it feels cheap. It raises questions, and most importantly, it disappoints your readers.

If you want your magic system to be believable, make it a tool, a power, but not the solution. If magic does save the day, make your characters work for it (like finding a relic, learning, training, or putting effort into invoking it).

2. Limit your magic users' power

Another problem with magic arises when there are no laws, limits, or systems that govern it. This becomes an issue when we meet a character who can use it seemingly without restriction, resorting to it whenever a challenge arises.

This kind of depiction of magic leads to internal plot holes, such as: if the character has such powers, what’s to stop them from taking over the world? How do other people feel living among those with unlimited power, and how many times have they tried to get rid of them? Also, why would these omnipotent characters play by the rules like the rest of the regular people inhabiting their world?

What’s lost in this scenario is internal consistency, and even if your readers can’t pinpoint the problem directly, it will nag at them like a smudge on the very edge of their sunglasses.

Avoid it by limiting your character’s access to magic. Let them fail, let them mess up, let them struggle. It will make your characters more believable, the magic more realistic, and the readers less suspicious.

3. Give magic clear costs and limits

Working out requires energy. Work requires concentration. Magic is similar—it requires resources from the character practicing it.

When building the magic framework for your novel, consider what resources your characters draw from to use magic, and how those resources are replenished. Does casting a spell require the same focus as solving a complex mathematical equation? And how quickly would your characters tire if they had to cast one spell after the other?

This helps both with the previous point (provides limitations for magic usage) but also establishes a coherent system.

Questions that can help define the magical framework include: can magic wielders cast spells without pause until they hit a certain limit, or do they need a pause between each one? Is their spellcasting ability restored after a good night’s rest, or do they need to perform a special ritual to replenish it, like pray to a deity, connect to an energy source, or dance around with the toad-fairies?

4. Define the source of magic in your world

Magic might not make sense in our world, but it can make sense in the novel you’re writing. The name of the game is not to explain it in a way that matches the physics we know here on Earth, but to make it logical within your story’s own framework. We may not have magical crystals that charge the user with otherworldly abilities, but the world you’re writing might.

This doesn’t mean turning your book into the fantasy version of a hard sci-fi—you don’t need to break down the exact mechanics of how spells work until your readers feel like they're reading an instruction manual.

All you need is for magic to have a source in your world, an explanation, and some general knowledge people share about its origin.

Embedding magic into your fantasy world’s own “laws of physics” gives it boundaries and makes it believable within your book’s framework.

Final Thoughts

Writing fantasy gives you unlimited creative freedom, but with great power comes great responsibility, and yours is not to annoy your readers.

Your readers don’t need you to overexplain, but they do want inner consistency to make your magical universe feel believable.

So when building your magical system, give it:

• Rules

• Limits

• Source

• A way for characters to tap into it

And you’re on the right track to writing fantasy the right way.

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