Damage Type

Piercing

Attacks deal pierce damage. In melee, pierce attacks deal unresisted damage regardless of armor, representing the user targeting the unarmored gaps.

Bludgeoning

Attacks deal blunt damage. Enemies wearing light armor are resistant. Bludgeoning weapon attacks have favor when making attacks against plate armor and bypass plate DR.

Cleaving

Attacks deal cleave damage. Enemies wearing plate armor are resistant. Cleaving weapon attacks have favor when making attacks against chain armor and bypass chain DR. Can be used to effectively chop wooden objects like doors.

Slashing

Attacks deal slash damage. Enemies wearing plate or chain armor are resistant. Slashing weapon attacks have favor when making attacks against cloth armor and bypass cloth DR, as well as dealing double damage to unprotected flesh.

Note that armor interactions only affect foes wearing armor, and may interact differently against the strange creatures of the Underworld. Animated skeletons, for instance, resist all damage except for bludgeoning.