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 if the weapon has a greater striking rune and three dice if the weapon has a major striking rune. For instance, a rapier with a greater striking rune deals 2d8 extra 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.