Via Negativa

(Champions of Ruin, page 22, DnD 3.5)

[General]

You can channel greater amounts of negative energy into your infl ict spells.

Prerequisite

Ability to rebuke undead

Benefit

As a free action, you can spend one of your rebuke attempts to deal additional harm with an infl ict spell. You must spend the rebuke attempt before making the attack roll. If the attack roll succeeds, the infl ict spell deals an extra 1 point of damage per character level (maximum +20). If the attack roll fails, the rebuke attempt is spent and wasted.