YAOSC (Yet Another Old School Clone)
This is the art of doing extra damage to those you have caught off-guard. A successful Evasion save by the target reduces the effects by one step on the chart below.
1: Off-guard attacks do 1 extra damage.
6: As (4), but the target goes last in the next round.
8: As (6), but attacks do 2d6 extra damage.
10: As (8), but attacks do 3d6 extra damage and the target must make a Shock save or be unable to act in the next round.