You’ve learned to attack in a way that stymies the natural resistances common in outsiders.
Prerequisites
Favored enemy (outsider) ability.
Benefit
Your weapon attacks ignore a number of points of damage reduction equal to half your favored enemy (outsider) bonus. This feat allows you to ignore only damage reduction that is normally bypassed by chaotic-, evil-, good-, or lawful-aligned weapons. Against other types of damage reduction, this benefit is halved.
Against outsiders that match your favored enemy subtype, the amount of damage reduction you ignore is equal to your full favored class bonus.