Keen Strike

Improved Critical (PH) (unarmed strike) , STR 23, WIS 23, ki strike +3,

Your unarmed strike is considered to be a slashing keen weapon (and thus threatens a critical hit on a 19-20). (At your option, any unarmed strike can do bludgeoning damage instead, but it loses the keen quality.) This ability doesn’t stack with similar abilities (for instance, if some other effect has already granted your unarmed strikes the keen special ability).

Your unarmed strikes become as sharp as blades.