Why Your Magic Needs Rules

Don't you hate it when you're reading a story about mages and you're trying to figure out why they don't just use magic to get out of a problem? The apprentice has cast a fireball, used telekinesis to grab keys while in a cell, and took advantage of psychometry to get a clue from the killer's hammer, but then has a problem opening a door; while it's a nice nod to Vox Machina, it brings up a lot of questions about how your magic system works.

The problem here is that since the magic system doesn't have much in the way of rules it's going to be hard to create any sort of tension: Since your readers have no idea what the limits of your character are, there is a problem establishing any credible problem for that character. In order to create a credible problem, the audience needs to know what the limits of your character are; otherwise, they will rightly suspect that your character will pull a solution out of nowhere to solve the problem. You need to establish what the rules are in order to create problems for your character; no rules, no suspense.

So, let's establish some rules, okay?

[Two notes:

1. Yes, this applies just as much to situations involving high technology and psychic abilities as it does to magic. The problem you're trying to avoid is "abilities that kill suspense", and these abilities do exactly that; there's a reason you see cell phone towers disappear in the woods. By establishing rules on how they work, especially their limits, you can bring back the possibility of suspense.
2. This obviously doesn't apply if the entire point is to just have fun. Sometimes we all just want to let loose and kick butt; there's a reason so many action movies are popular. There's nothing wrong with just going for it and blowing all your problems away; if you want to write it, go for it. However, you're not worrying about tension in that situation so just do you.]

Establish The Rules Early & Use Them

You need to keep in mind that whatever rules you establish, you need to establish them early, even if you just allude to them. If you establish them too late, such as after the beginning of the third act, then they feel tacked on and won't do the job of helping with your tension issue. If you're going to establish any rules, at least do so (even indirectly) in the first act.

The obvious corollary is that you need to remember to use them against the character. If you go through the paces of establishing the rules but then never use them, then they won't really help build your tension level. So not only do you need to establish the rules but then use them against the character; if you don't let one shoe drop while dropping the other, then your story will suffer for it.

The Use of Magic Items

This also means that magic items need to be regulated as well. Magic items, even powerful artifacts from previous ages, need to be focused on a set number of uses, be it something like three times per day or even twenty uses before it runs out of juice. Obviously, some items can be used as often as you would like, like a sword that never dulls, but they need to be very focused items. The key here is that you're trying to set up a system that encourages tension; a wand of fireballs with limited charges can run out in the worst situation while a ring of infinite wishes will always kill your tension level or create forced situations, which are just as bad.

The Vancian System

When you look at role-playing games, there are a lot of reasons the D&D game has been around for so long; one of those reasons is the Vancian magic system it uses, based on that presented in Jack Vance's Dying Earth books. The basic idea is that mages must memorize the spells they want to cast and that they can only memorize so many spells; also, once a memorized spell has been used, it is wiped from the mage's memory (nothing prevents a mage from memorizing multiple iterations of the same spell). The character can memorize their spells whenever they want, but they are limited to memorizing their spells just once a day (such as when they wake up or at sunset).

Not only does this limit how many spells a mage can cast, but it also encourages a mage to memorize different "lists" of spells, such as ones for combat, adventuring, going to market, entertaining guests, or even cleaning the house. Consider the fun that could ensue if a mage had nothing but cleaning spells memorized but then had to fend off a ninja attack; a feather-dusting spell would need to be used very carefully to be effective there.

The Elemental Focus

This is such a cliché that it hardly needs an introduction, but it's worth considering, especially if you widen the elements it can work with. The character is limited to their experience but otherwise is only limited by what the element allows. You should try to avoid getting too abstract with this or you're right back to Square One; an element that's too useful or has a wide range of applications will kill a lot of the tension because readers will be expecting it to get the character out of trouble with little actual effort on his part.

The Item Focus

While this is pretty familiar to Harry Potter fans, it should be familiar to those who follow folklore as well. The idea is pretty simple: The character needs access to the right item to cast spells, with some spells requiring specific items; the mage can probably cast most of his spells with his standard wand, but to cast flight requires his enchanted broom, for example. You can also generalize this to other situations, such as times ("the portal spell can only be cast during an eclipse"), locations (portals to the elemental planes can only be cast in areas where there is a lot of the element in question), or even specific materials (you need a bit of web to summon spiders).

It should be noted that role-playing games sometimes require specific gestures, words, or even materials to cast spells; this can be another type of required focus. In these cases, binding or gagging the character can prevent them from casting spells, as can stealing the materials (or the pouch carrying the materials) or if the mage runs out of the material, especially if it was rare or expensive.

Power-Robbing Items and Situations

These are just situations where magic doesn't work as it should: dead or wild magic zones, creatures that are immune (or at least resistant) to magic or specific types of magic, items or creatures that steal magic power, and even items that can disrupt or cancel magic. If these are rare, they won't really help you; their appearance will feel coincidental and you want to avoid coincidence as much as possible. By the same token, if they are too common then there is the question of why anyone would practice magic in the first place.

So have them, but make them uncommon and you should be okay.

The bottom line is that magic is a major force and one that allows writers to have a lot of fun with their worlds; it allows you a way to break the rules and show the wonder of your world. However, magic needs some limits to work as part of the world; you need to find a balance between making it a predictable force of the world while allowing it to act as a force for creation and wonder. Your goal as a writer should be to figure out where that balance lies and revel in it. Once you find that balance, it becomes a tool that allows you access to some pretty fun concepts, allowing you to really explore your world and its story.