The Resolution Engine
Nearly every uncertain action uses one engine: roll d100 against an effective percentile value. Equal to or under the value succeeds; above it fails. Apply circumstances first, then cap the effective value between 1 and 100.
Result bands
Check for a fumble before reading success. Rolls of 96–100 always fumble, even when the target is high. For all other rolls:
| Result | Threshold |
|---|---|
| Critical | At or below one-twentieth of the effective value, minimum 1 |
| Special | Above Critical and at or below one-fifth |
| Ordinary | Above Special and at or below the effective value |
| Failure | Above the effective value |
Use the same bands for skills, characteristics, combat, Stability, casting, and improvement checks. A critical should be an exceptional success, not merely extra damage; a fumble should introduce a complication rather than erase the scene.
For opposed checks, the better success band wins: Critical, Special, Ordinary, then Failure. If both have the same band, the lower roll wins. If both fail, the roll closest to the target wins. A fumble loses unless both fumble.
Modifiers and dice
The standard difficulty ladder is Routine +20%, Standard +0%, Difficult −20%, Hard −40%, Extreme −60%, and Near Impossible −80%. Use a modifier when circumstances are the important variable. Use a bonus or penalty die when the whole situation is broadly favorable or unfavorable: roll twice and keep the lower or higher result respectively.
Do not stack several small bonuses merely to reward description. One clear advantage is enough. Preparation can instead remove a roll, reveal a clue, supply a tool, or turn a Hard task into a Difficult one.
Luck is a player-facing safety valve. A point can reroll a failed action or add +20% to one check; routine tasks can be treated as automatic successes when the character has time and no meaningful danger. Luck refreshes after a full night's rest. Preserve the tradeoff: spending Luck now should make later danger more frightening.
Designing new mechanics
Before adding a mechanic, answer three questions:
- What decision does it create?
- Which existing value or skill should interact with it?
- What happens on success, failure, and fumble?
If the answers are just “roll another special die,” the rule probably belongs as a modifier or consequence inside the existing engine. Consistency is a feature: players should be able to predict the shape of an unfamiliar rule even when its fiction is strange.