Enervation

You point your finger and fire a black ray of negative energy that suppresses the life force of any living creature it strikes. You must make a ranged touch attack to hit. If you hit, the subject gains 1d4 temporary negative levels (see Special Abilities). Negative levels stack.

Assuming the subject survives, it regains lost levels after a number of hours equal to your caster level (maximum 15 hours). Usually, negative levels have a chance of becoming permanent, but the negative levels from enervation don't last long enough to do so.

An undead creature struck by the ray gains 1d4 × 5 temporary hit points for 1 hour.