Magic or technology system with rules and costs

Design a fantasy magic or sci-fi technology system with clear rules, real costs, limits and story-ready consequences.

Change note: Initial version

Prompt

Help me design a {{systemtype}} for my story.

Genre and world: {{world}}
Who can use it: {{users}}
The central theme it should reflect: {{theme}}
Story needs: {{needs}}

Provide:
1. The core principle in two sentences, and the one-sentence rule a reader could repeat.
2. How it works: sources, methods, training or tools, and what it looks like in use (sensory details).
3. Costs and limits: at least three firm limitations, and a cost that hurts the user personally or socially. Explain how the costs create drama instead of removing it.
4. Society impact: how it shapes economy, law, class, warfare, religion and daily life. Include one surprising, mundane use.
5. Failure modes and loopholes: how it can go wrong, be abused or be exploited cleverly by a determined character.
6. Three scenes the system makes possible, and three plot shortcuts it must never allow.
7. Five open questions I should resolve before writing.

Prefer a small number of strong rules over a long list of exceptions. Avoid generic elemental schemes and power rankings unless the theme calls for them.

Variables

• {{systemtype}}System typeselect

  Options: Magic system, Sci-fi technology, Psychic abilities, Religious miracle, Alchemy or crafting

  Default: Magic system

• {{world}}Genre and worldlong

  Default: A low-fantasy trading empire where seasons are unstable

• {{users}}Who can use ittext

  Default: Anyone who can afford the training, but few can afford the cost

• {{theme}}Central themetext

  Default: Debt and what people owe each other

• {{needs}}Story needstext

  Default: Must create tension in negotiations, not just fights

Example output

**Core principle:** Magic is borrowed from the future. Whatever is done now must be repaid by the caster, in kind, later. Rule: "Every working is a loan."

**How it works:** Casters speak a promise aloud, naming what they will return, and the world bends. Light, warmth or a lifted load appears as a faint shimmer that smells of cold metal.

**Costs and limits:**
- The repayment is exact and arrives within one season.
- Unpaid debts transfer to family.
- Only what could plausibly be done by effort can be borrowed; no creating from nothing.
- Cost: reputation. Banks of "ledger-keepers" track every caster's debt.

**Society:** Merchants hire casters but require collateral; a heavily indebted caster is a social pariah. Mundane use: borrowing a warm winter for a single wedding.

**Loopholes:** Naming a debtor who agrees to repay for you.

**Scenes it enables:** a negotiation where both sides check each other's debt records; a caster forced to repay with years of sight; a heist built on an unpaid promise.

**Never allow:** instant resurrection; unlimited free power; rescues without a price.

**Open questions:** Who audits the ledger-keepers? Can a nation hold debt?

Notes

Requiring a theme and a personal cost keeps the system from becoming a power list. Ask the model to stress-test it by writing three ways a clever villain could break it.