To make a magic system, decide three things before you write a spell: what it can do, what it costs the person using it, and what it cannot do. Write the last two down first. Brandon Sanderson's Second Law of Magic says it in four characters, Limitations > Powers, and the rest of this page is a way to apply it: a one-page ledger, a worked example from a book you can read for free, and a count of how often older fantasy bothered to state its rules.
What the usual advice says (checked November 2026)
| Source | What it gives you |
|---|---|
| Dabble (25 Oct 2023) | Hard vs soft magic, abilities and limits, power sources, costs, a six-step build, tips against deus ex machina. |
| Jane Friedman (23 Jul 2024, updated 18 Feb 2025) | Role of magic in the story, hard/soft, source, limits, plus a fill-in template for magical creatures and question lists. |
| Well-Storied (undated) | Six steps: use, users, limitations, dangers, origins, culture. |
All three agree on limits, and none of them shows a limit working inside a real book. That's the gap this page fills.
Sanderson's two laws, in his words
From his own site, read 11 November 2026 (the essays carry no publication date on the page):
- First Law: "An author's ability to solve conflict with magic is DIRECTLY PROPORTIONAL to how well the reader understands said magic."
- Second Law: "Limitations > Powers." He explains it with Mistborn: the practitioners can move things with their minds, "however, there are two important limitations. The objects must be metal" and they can only push directly away or pull directly toward themselves. And with Robert Jordan: men who use the magic "go slowly insane. This cost is wonderful, as it makes the magic worth something."
Put together, they give a working rule: the reader may only be rescued by a power they've already seen the edges of. If the edges aren't on the page, the rescue feels like cheating.
The one-page magic ledger
Fill in one line per rule. If you can't write the "Cost" and "Cannot" cells, the magic isn't designed yet.
| Rule | Who can do it | What it does | Cost (paid by whom, when) | Cannot | Where the reader first sees the edge |
|---|---|---|---|---|---|
| chapter / scene |
The last column is the First Law as a checkbox. A power that solves the climax needs an entry there well before the climax.
Worked example: the Golden Cap in The Wonderful Wizard of Oz
Baum's 1900 book is a soft-magic fairy tale, and it still contains a textbook rule. From the Project Gutenberg text: "This Golden Cap had a charm. Whoever owned it could call three times upon the Winged Monkeys, who would obey any order they were given. But no person could command these strange creatures more than three times."
Filled into the ledger:
| Rule | Who | Does | Cost | Cannot | Edge shown |
|---|---|---|---|---|---|
| Winged Monkeys obey the Cap's owner | Whoever holds the Cap | Any order the owner gives | Three uses in total, ever | Be used a fourth time | Stated outright when the Witch reaches for it |
Then the book spends the cost on the page. The Witch has used two commands already: "Once was when she had made the Winkies her slaves", the second "when she had fought against the Great Oz himself". "Only once more could she use this Golden Cap, for which reason she did not like to do so until all her other powers were exhausted." She spends the last on Dorothy; the Monkey leader says, "You have called us for the third and last time." Dorothy then takes the Cap over, and the count goes on: when she calls them to cross the desert, they can't, and she says, "I have wasted the charm of the Golden Cap to no purpose." Later the Monkey King tells her, "This is the last time you can summon us." The limit makes each use a decision, and the reader keeps the count without effort.
The Silver Shoes work the same way. The Witch steals one and gets only "half the power of their charm", and Dorothy "could not use it against her". A partial item is a limit with a plot attached.
How often old fantasy states its rules (our count)
We ran nine public-domain fantasy texts from Project Gutenberg through a simple script: split into sentences, and count those that name magic (magic, spell, enchant, bewitch, sorcer-, witch, wizard, conjur-, charm, wand). This measures how much a book talks about magic, not how good its system is, and it misses magic that goes by other names (fairies, wishes, Peter Pan's dust). Counted 11 November 2026.
| Text | Words | Sentences naming magic | Per 10,000 words |
|---|---|---|---|
| The Wonderful Wizard of Oz (1900) | 39,649 | 203 | 51.2 |
| The Marvelous Land of Oz (1904) | 41,878 | 142 | 33.9 |
| Grimms' Fairy Tales | 101,111 | 75 | 7.4 |
| Phantastes (1858) | 69,123 | 32 | 4.6 |
| The Well at the World's End (1896) | 225,427 | 48 | 2.1 |
| Le Morte d'Arthur (1485, both volumes) | 362,068 | 61 | 1.7 |
| The Life and Adventures of Santa Claus (1902) | 30,049 | 5 | 1.7 |
| Peter Pan (1911) | 47,268 | 6 | 1.3 |
| The Princess and the Goblin (1872) | 51,874 | 0 | 0 |
Two things stand out. The Oz books talk about magic five to forty times more than the rest, and they are also the ones with explicit counted limits: the Cap's three commands, the Shoes' half power, a ban on witchcraft that Mombi breaks and the Good Witch had forbidden. The texts that mention magic least, Morte d'Arthur and The Well at the World's End, leave it unexplained: Launcelot says he knows not how he came into the castle "but it be by an enchantment." That works as atmosphere. It can't solve a plot, which is Sanderson's First Law seen from the other side. (We then read every sentence our script flagged for cost or limit words: apart from the Oz and Grimm examples above, the matches were mostly "cannot" in ordinary speech, so we don't report a percentage.)
Choose hard or soft, then keep to it
Hard magic has stated rules and the story can lean on them. Soft magic is mysterious and the story can't. Neither is better, but the rule is the same: a soft system must not rescue the hero. Use soft magic for wonder and threat, hard magic for solutions. Mixed books work when each power is labelled by which kind it is. Dabble and Jane Friedman both make this split; use their lists for types and sources.
Five questions that catch most magic-system holes
- Who pays? The user, someone else, the world? A cost nobody pays isn't one.
- When is it paid? Before, during, after? Paid later means the bill can arrive in the plot.
- Can it be run out of? Three uses, a day's worth, a body part, years of life.
- What does the villain's version look like? The same rule, abused, is the best antagonist.
- What can an ordinary person do about it? If the answer is nothing, your magic has no stakes.
Keeping the rules straight across a whole book
The usual failure isn't a bad system, it's drift: the cost that mattered in chapter 3 is forgotten in chapter 25, or the limit quietly loosens because the scene needed a rescue. Keep the ledger beside the manuscript and read it before every scene that uses magic.
In KudoWrite you can enter each rule and its cost as a story-bible entry with its aliases. The engine picks the entries a passage needs before it writes, and the bible and the running summary of the whole book keep up as you write, so a count like the Golden Cap's (two used, one left) is in front of the writing model when chapter 30 arrives. Open a book, add the ledger rows as your first bible entries, and write the scene where the magic costs her something. KudoWrite is a browser app with an English interface, one free credit to try it, then one-off credit packs. Related reading: what a story bible is, writing a novel with AI and why AI forgets your story.