Bane Black Sky (3.5e Feat)
From D&D Wiki
Bane Black Sky [Dark]
The combination of your hatred for a specific creature type and the darkness that dwells inside of you, your black sky class feature damages those of that creature type more heavily.
Prerequisite: Darkness Class Feature, Black Sky Class Feature
Benefit: You deal additional damage with your black sky to creatures of your chosen creature type, use the favored enemy table for your choice, as if the amount of hit points you sacrificed was equal your charisma score higher. (ex. if you have a charisma score of 10 and you sacrifice 16 hit points for your black sky class feature and your bane is for Humanoid(elves), then you would deal damage equal to half of 26 hit points rather than the actual amount of 16 hit points that you had sacrificed to elves.)
Normal: Normally you would do the amount of hit points sacrificed as damage.
Special: You may take this feat multiple time, each time choosing a different creature type.