Magic System Generator

A magic system is a set of promises

Readers do not need to understand your magic, but they need to trust it. A system makes a promise: this is what it can do, this is what it cannot, and this is what it costs. When the hero is in trouble, the reader wants to know whether the magic can help. If it can do anything, there is no tension. If its rules are clear, the hero has to be clever, and the reader gets to enjoy the cleverness.

Each result gives you four things to keep that promise. The source says where power comes from, which tells you who has it and who is cut off from it. The rule says how it is used, which tells you what a scene of magic looks like. The cost says what a practitioner gives up, and the limit says what the world will not allow.

Cost and limit do different jobs

A cost makes magic personal. It gives the caster something to lose each time, and a character who is tired, forgetful or cold in a crisis is more interesting than one who is simply powerful. Choose costs that you can show in a scene, such as a shaking hand or a missing name, because a cost the reader never sees is not a cost.

A limit makes magic useful as a plot tool. If magic can never undo a death, every death in your story carries weight. If it cannot touch iron, iron becomes a weapon, a prison or a currency. The limit is where your worldbuilding begins, because the people of your world will organise their lives around what the magic cannot do.

Let the society follow the system

The last piece is what the magic does to the world. If it costs a day of a practitioner's life, who pays that price, and who profits from the work? If it is a family secret, who is left out? Pick one social consequence and follow it for three steps: the law it produces, the crime it makes possible and the person who is caught between them. That is a setting and a plot in one.

Finally, test the system on a problem. Ask how it would solve a locked door, a plague and a war. If it solves all three, add a limit. If it solves none, add a use. A good system gives the hero a way to try and a reason to fail.

Ten example magic systems

• Natural world Magic comes from the memory held in stones. To use it, a practitioner can create nothing, only change what already exists. Each spell costs the caster a memory of the caster's own choosing. It can never undo a death.
• Natural world Source: the pull of the moon on water. Rule: the user must stay within sight of running water. Cost: a measure of their sleep. Limit: it can never take effect beyond the next full moon.
• Natural world In this world, magic comes from the seasons themselves, borrowed a day at a time. Because of this, a guild decides who is allowed to cast. To use it, each act must be paid for before it is performed, and each spell costs the caster a year of luck.
• Body and mind Magic comes from the years of a person's own life. To use it, the user must be willing to be changed by it. Each spell costs the caster a day of the caster's life. It can never change the past. Because of this, the old are more powerful than the young, and are treated with fear.
• Body and mind Source: the dreams of the sleeping. Rule: a practitioner must touch whatever they change. Cost: their own reflection. Limit: it can never act on a person who is asleep.
• Body and mind In this world, magic comes from a single memory given up for every spell. Because of this, mourning is a profession. To use it, the user must first give a true name, their own, and each spell costs the caster a name that they will never remember again.
• Words and bargains Magic comes from promises made aloud. To use it, every spell must be spoken from beginning to end without a breath. Each spell costs the caster a promise they made, which is broken. It can never make anyone fall in love.
• Words and bargains Source: debts that others owe each other. Rule: a practitioner must hold something that belongs to the target. Cost: something they love, which cannot be recovered. Limit: it can never work on iron.
• Objects and machines Magic comes from the old engines buried under the city. To use it, the user must stay awake, because the effect lasts only as long as they do. Each spell costs the caster their steadiness, so that their hands shake for an hour. It can never change anything that was made by a practitioner. Because of this, the poor sell small pieces of themselves to the wealthy.
• Objects and machines In this world, magic comes from bells cast for a purpose. Because of this, people keep their true names secret. To use it, the spell must be written down and then destroyed, and each spell costs the caster the sound of a loved one's voice.