This spell enables the caster to drain the "life force" out of undead within the area of affect, and do one of two things with it. First, you can channel the energy in a lightning bolt fashion(except that this is invisible). This does 1d4+1 points of damage per level. Or, you may choose to use the reverse of the first option ad give someone 1d4 h.p. per level. Any additional h.p. goes away after one hour. This does, however have a nasty side affect. The recipient of this spell is afflicted with a horrible stomach sickness 1d6 hours later. They are reduced to one h.p. and are unable to do anything but sit in bed for two weeks.
The material component of this spell is a black onyx prism worth at least 10,000 gp.