Enervation

Enervation is a necromancy spell that severely weakens the subject.

Effect
You point your finger and utter the incantation, releasing a black bolt of crackling negative energy that suppresses the life force of any living creature it strikes. You must make a ranged touch attack to hit. If the attack succeeds, the subject gains 1d4 negative levels.

If the subject has at least as many negative levels as HD, he dies. Each negative level gives a creature the following penalties: -1 competence penalty on attack rolls, saving throws, skill checks, ability checks, and effective level (for determining the power, duration, DC, and other details of spells or special abilities). Additionally, a spellcaster loses one spell or spell slot from her highest available level. Negative levels stack.

Assuming the subject survives, he regains lost levels after a number of hours equal to your caster level. Usually, negative levels have a chance of permanently draining the subject's levels, but the negative levels from enervation don’t last long enough to do so.

If the ray strikes an undead creature, it gives that creature 5 temporary hit points per two caster levels (maximum 25 temporary hit points).