There are two documents open on the desk tonight. On the left monitor, a build sheet: columns of numbers, a scaling curve, one cell highlighted in yellow because it does something it shouldn’t. Beside the keyboard, a printed chapter with a pen lying across it, uncapped, where I stopped reading mid-paragraph because a character did something that no sensible practitioner of this magic would ever do.
They are the same problem. I just hadn’t noticed until I put them next to each other.
The Claim
Every magic system is a build space: a set of choices a practitioner can make, each with costs and returns. Players have a name for the discipline of exploring that space on purpose. They call it Theorycrafting. They sit down with the rules, ask what the strongest possible use of them looks like, and then report what they found.
Writers rarely do this to their own systems. They design the rules, write the scenes, and wait for a reader to discover the seam. The reader will, because readers are optimizers by temperament: the moment a story shows a character solving a problem with magic, someone in the audience asks why they didn’t just do the stronger thing.
The working claim of this post: a magic system should be stress-tested the way a build is, by asking what a motivated optimizer would do with it, before a reader asks it for you.
That single question is the whole tool. Call it the Optimizer’s Question:
If a smart, motivated practitioner spent twenty years optimizing this system for survival and advantage, what would they be doing?
The answer tells you what your world should look like. And it tells you what your protagonist is choosing against.
Four Terms From the Build Sheet
Theorycrafters carry a small vocabulary that transfers cleanly to fiction.
Dominant strategy. An option so reliably strong that choosing anything else is a mistake. Games treat these as bugs, because they collapse a build space into one answer. Fiction should treat them as facts about the world. If a dominant strategy exists in your system, then everyone in the setting who is paying attention would use it, and their culture would be built around that choice.
Breakpoint. A threshold where adding a little more of something changes the kind of thing you can do, not just how much. Two rings versus three. Ten feet versus eleven. A breakpoint is where a system stops scaling smoothly and starts producing new behavior, which makes it a place where stories happen.
Opportunity cost. What you give up by choosing this option instead of another. This is the term that makes choices real. A strength with no opportunity cost isn’t a choice; it’s a free upgrade.
Degenerate combination. Two rules that are individually reasonable and jointly broken. Games find these constantly, because the number of possible pairings dwarfs the number a designer can check by hand. Prose systems have them too; the difference is that nobody is paid to look for them.
A Short Case: The Ring Ledger
Here is a small hypothetical to run the question on. Call it the Ring Ledger.
The rule: a practitioner can bind a single charge of power into a ring. Each ring holds one charge. A charge, once spent, refills at dawn. A practitioner can wear any number of rings.
It reads as a tidy little system. Now ask the Optimizer’s Question.
The first thing the optimizer notices is that the rule has no cap on rings. That is a dominant strategy waiting to happen: wear every ring you can afford. The system’s real constraint isn’t power; it’s jewelry. Practitioners with money wear a dozen rings. Practitioners without money wear one. The magic is a wealth multiplier, and your setting’s class structure should show it.
The second thing the optimizer notices is the breakpoint. One charge is a trick. Three charges are a skirmish. Twelve charges released in the same breath are a different kind of event altogether, and a duel between two practitioners with a dozen rings each is a question of who can spend charges fastest, not who has more. The scaling is not smooth. Somewhere around the point where a practitioner can end a fight in one exchange, the whole culture of fighting changes: ambush becomes the only rational tactic.
The third thing is opportunity cost, and here the system is quiet, which is a warning sign. If wearing more rings costs nothing, then there is no decision in the system. So either the rule needs a cost (weight, interference between rings, a bodily toll when more than a few are charged) or the story needs to accept that the strongest option is simply the one everyone takes.
The fourth is the degenerate combination. Suppose your setting also contains a way to refill charges faster than dawn. Each rule is reasonable. Together, they produce an unlimited battery.
None of this required a single scene. It took four questions and about five minutes, and it has already revealed the setting’s class structure, its fighting culture, a design hole, and a combination that would have wrecked the third act.
Reading It Two Ways
The interesting part of a dual-room approach is that the same analysis serves two different readers.
As a player, you are looking for the build: the strongest line through the rules, the breakpoint worth chasing, the opportunity cost you are willing to pay. The result is a plan for what to do.
As a writer, you are looking for the culture: the world that would grow up around the strongest line, and the character who chooses against it. The result is a description of what people already do, and why your protagonist does something else.
What connects them is the idea that the build space is a map of motivation. A character who takes the dominant strategy is conforming to the world. A character who takes a suboptimal build is making a statement, and the story needs to know what the statement is. If your hero uses a single ring in a world that rewards twelve, the reader should be able to tell whether that is poverty, principle, or a flaw.
This is where theorycrafting becomes characterization. The numbers are not the story. They are the pressure the story pushes against.
Where the Method Breaks
Min-maxing the novel. The Optimizer’s Question is a diagnostic, not a drafting method. A manuscript that trails a spreadsheet’s logic will read like one. Run the pass in your notes, keep the culture it implies, and show the reader only what the scene needs.
Balancing the personality out. Games exist under a pressure that fiction does not: they must be fair to the player. Fiction is allowed to be lopsided. A magic system in which every option is equally strong is a system with no flavor. Asymmetry is where a setting’s character lives. A dominant strategy that is reviled, ruinous, or ruinously expensive socially is better material than a perfectly balanced menu.
Assuming everyone optimizes. Players optimize because the game rewards it. People in a world optimize for survival, status, and comfort, and they are bad at it in ways that are useful to a writer. The question asks what the best option is; it does not require that everyone find it. A world where the dominant strategy exists and most people haven’t discovered it is a different, and sometimes more interesting, world than one where everyone has.
Mistaking a patch for a plot. Games fix degenerate combinations with updates. A writer can do something similar by quietly removing an overpowered rule between drafts, but the cleanest cases leave the removal visible. Harry Potter’s Time-Turners are the standard illustration of a rule that would have broken the series’ stakes, and the books deal with it by destroying them within the story. Treat a broken combination as an event the world has to explain, not an erasure you hope nobody noticed.
The Last Page
The build sheet and the chapter on the desk were never two different documents. One of them asks what is possible. The other asks who chooses what, and what it costs them. The most useful thing you can do for a magic system is let those two questions argue in the margins before the manuscript is finished.
Sanctuary Project
Take one magic system you are working with: your own, or one from a book or game you know well. Write the Optimizer’s Question at the top of an index card, then answer it in a single paragraph: what the twenty-year optimizer is doing, how many resources they hold, and what everyone around them has organized their lives to avoid or imitate.
On the back of the card, write one sentence for your protagonist: the dominant strategy is X, and she doesn’t take it because…
If you can finish the sentence with something specific, you have a character. If you can’t, you have found the next scene to write.