Tests
When an action is risky, and its outcome uncertain and important, a relevant attribute should be Tested. A Test succeeds if:
1d20 + Score ≥ 20
This is mathematically equivalent to Roll Under systems, but retains the expectation that higher numbers are better. An average score of 10 has a 55% chance of passing a Test. For each additional point, this chance increases by 5%.
Often, a Test (and therefore risk) can be avoided with good planning or by detailed, diegetic interaction with the fiction. Additionally, PCs are assumed to have basic competency in adventuring and therefore do not Test for simple tasks like climbing a rope, swimming in calm waters, or reading common script.
Saves
When a Test is triggered in reaction to an event in the game world, rather than proactively by a player’s action, it is called a Save. A Save is a character’s final, undeserved chance to avoid a bad outcome, and is therefore more difficult than a Test. A Save uses half the attribute’s score (rounded down) and succeeds if:
1d20 + (Score / 2) ≥ 20
Anytime a character fails a Save, they suffer 1 Stress
Boons and Banes
Boons are granted when circumstances or player actions make a Test more likely to succeed. Conversely, Banes are imposed when conditions make a Test more prone to failure. The target number never changes: it is always 20 regardless of difficulty.
Boons and Banes may stack from different sources and cancel each other out, one to one. For each net Boon or Bane, roll 1d6 and note the highest value among them. If the d6s are Boons, add this value to the Test result. If the d6s are Banes, subtract this value instead.