D&Dtools1

You can sacrifice life force to increase the damage you deal.
Once each round, as a free action, you can sacrifice up to 10 of your hit points (doing this does not trigger an attack of opportunity).
For every 2 hit points you sacrifice, on your next successful attack you deal +1d6 damage, to a maximum of +5d6 on that attack.
Your ability to deal this additional damage ends when you successfully attack or when the spell duration ends.
You can make as many sacrifices as the spell duration allows.
Sacrificed hit points count as normal damage.
For example, an 8th-level paladin can cast this spell with a duration of 4 rounds.
If she sacrifices 10 hit points a round and hits in every round, she can spend up to 40 hit points and deal up to +20d6 points of additional damage.