Deadly
Source Player Core pg. 256
On a critical hit, the weapon adds a weapon damage die of the listed size. Roll this after doubling the weapon's damage. This increases to two dice for elite and ultimate grade weapons and 3 dice for paragon grade weapons. For instance, an elite nano-edge rapier deals an additional 2d8 piercing damage on a critical hit. An ability that changes the size of the weapon's normal damage dice doesn't change the size of its deadly die.