Utterdark Blast

Warlock Invocation
Level: Dark, 8th
Components: V, S
Casting Time: 1 standard action
Range: 60 feet
Duration: 1 hour (For neg levels)
Saving Throw: Fort for 2 neg lv
Spell Resistance: Yes

Your eldritch blast does negative enrgy damage which heals undead instead of damaging them. Any creature struck must make a fortitude save or take two negative lvls, these negative lvls fade after one hour.

(Complete Arcane, Page 134)