Extreme Prejudice

Combat

Your hatred of a particular type of creature has honed your killer instinct.

Prerequisite: Seething Hatred†, sneak attack +3d6, studied target† class feature.

Benefit: When you succeed at a sneak attack against a creature you selected as the target of your Seething Hatred feat, you use d8s to roll sneak attack damage instead of d6s.

Source: Advanced Class Guide