D&Dtools1

A touch from your hand, which crackles with black energy, weakens the life force of living creatures.

Each melee touch attack you successfully make during the spell's duration channels negative energy that bestows one negative level on the target and grants you 5 temporary hit points. This spell cannot give you more temporary hit points than your normal starting hit points (your hit point total cannot exceed two times your normal starting hit points). Both the negative level and the temporary hit points last for up to 1 hour. You can use this attack once per round for a number of rounds equal to your caster level. Any charges of the spell not used by the time the duration expires are lost.

An undead creature you touch instead gains 5 temporary hit points and you lose a like amount (no save). Temporary hit points gained in this way last for up to 1 hour.