Your spells channel negative energy to deal extra damage to living creatures, but are less effective against unliving opponents.
Prerequisites: Nongood alignment, must not have the ability to turn undead.
Benefit: Your spells are infused with negative energy. An enervated spell deals an extra 50% damage to living creatures, but deals 50% less damage to constructs, undead, and objects.
An enervated spell uses up a spell slot two levels higher than the spell’s actual level.
Special: A character who has the ability to channel positive energy to turn undead cannot select this feat.
Source: Libris Mortis, page 26.