A hit that strikes a vital area and therefore deals double damage or more. To score a critical hit (crit), an attacker must first score a threat (usually a natural 20 on an attack roll) and then succeed on a critical roll (just like another attack roll). Critical hit damage is usually double damage, which means rolling damage twice, just as if the attacker had actually hit the defender two times. (Any extra damage dice, such as from a rogue's sneak attack, are not rolled multiple times, but are added to the total at the end of the calculation.)