Critical hit

• A critical hit occurs randomly (with a 1-in-11 chance, subject to certain modifiers) when hitting with a ranged or melee attack. It increases the amount of damage you deal to your opponent. Specifically, it doubles the weapon power component of the damage:

 weapon damage = (a term based on your stats vs. monster's defense) +
                 (10% to 20% of mainpower) * crit * tsfactor        +
                 (10% to 20% of offhandpower)                       + 
                 (bonus melee damage)                               +
                 (bonus elemental damage)

Where

• crit is 1 for a normal hit, and 2 for a critical hit, and
• tsfactor is 1 for a normal attack, 2 for a Thrust-Smack, and 3 for a Lunging Thrust-Smack.

• For a comprehensive list of all items that affect the critical hit percentage, see Critical Hit Chance.

Monster Critical Hits

Monsters can critical hit too -- but a monster critical hit doesn't cause you any extra damage; it just succeeds in hitting when it otherwise would have missed. Monster critical hits, like monster fumbles, occur with a 1/22 (4.5%) chance per round. Thus, the total chance of abnormal monster behavior in any given round is 1/11, the same as player critical hits.