The Core Mechanic: Whenever you attempt an action that has some chance of failure, you roll a twenty-sided die (d20). To determine if your character succeeds at a task you do this:

If the result equals or exceeds the target number, your character succeeds. If the result is lower than the target number, you fail.

Dice rolls are described with expressions such as '3d4+3,' which means 'roll three four-sided dice and add 3' (resulting in a number between 6 and 15). The first number tells you how many dice to roll (adding the results together). The number immediately after the 'd' tells you the type of die to use. Any number after that indicates a quantity that is added or subtracted from the result.

d%: Percentile dice work a little differently. You generate a number between 1 and 100 by rolling two different ten-sided dice. One (designated before you roll) is the tens digit. The other is the ones digit. Two 0s represent 100.