Static bonuses sometimes apply to rolls. Static bonuses of the same type (such as two insight bonuses) do not stack. Instead, the highest bonus applies. The one exception to this is untyped bonuses. Untyped bonuses do stack.
Twenties explode. If the initial roll comes up 20, the die is rerolled and the new result added to the old. Rerolls continue for as long as the die continues to come up 20.
Ones implode. If the initial roll comes up 1, the die is rerolled and (21-the new result) subtracted from the old result. Rerolls continue for as long as the die continues to come up 1.
Margins of Success and Failure sometimes apply to rolls. When making a check, look at the Margin Rate listed with it. For each margin rate by which a result beats a DC, you score a margin of success. For each margin rate by which a DC beats a result, you score a margin of failure. Margins of success and failure have special effects, outlined in each specific skill use. On opposed checks, each side is assigned a DC, and whichever side had the most margins of success and the fewest margins of failure wins the check. Treat the margin of success rating as the difference between each side's margins of success, treating a margin of failure as a negative margin of success.
There are two ways to "buy" a margin of success. The first is to attempt something beyond the ordinary. For each two margin rates over the base DC that the character increases the DC before rolling, three margins of success are added in the event that the character succeeds.
The other way can only be applied to checks on which a margin of success and a margin of failure do not contradict one another (that is, uses with the line “Contradiction: No”). The character tries to push themselves to the cutting edge, foregoing ordinary caution and taking bizarre risks to do something spectacular. For each margin of failure the character willingly accepts before rolling, a margin of success is added if the character succeeds.
If a change to a number (other than a check's final static bonus) would change its sign, instead change the number to 0. Multipliers add, so two doublings is a tripling, a tripling plus a doubling is a quadrupling, and so on.
A skill check is 1d20+the character's associated ability+the character's skill+modifiers.
In combat, attacks are made using the appropriate Attack skill in an opposed check against the opponent's Defend skill. Each Defend has specific conditions and effects attached to it:
- Defend (dodge) requires that the defender be able to move freely. Only dodge and resist may be applied to touch attacks.
- Defend (block) requires that the defender be able to move freely and be carrying some form of weapon. A blocked attack triggers attacks of opportunity that, if themselves blocked, do not trigger attacks of opportunity.
- Defend (resist) has no attached conditions and no special effects.
Die sizes are upgraded as follows: d2 (coin or 1d4/2), d3 (1d6/2), d4, d6, d8, d10, d12, d12+d2. In the final item, the d2 may itself be upgraded. Note that at no point does the upgrade reach d20.