The spell healed undead creatures. Even incorporeal ones could be touched with this spell. The spell protected the caster from any adverse effects from touching an undead creature.
The reversed version of this spell was called drain undead and hurt undead creatures. While the name of this spell included drain, the spell did not convert the drained energy from an undead into a beneficial force for the caster. This version also protected the caster like undead regeneration.
Both versions allowed only undead creatures as targets.
The spell required only somatic and verbal components.