[Exalted]

You can increase the intensity of the light surrounding you to damage undead creatures.

Prerequisite: Nimbus of Light, CHA 15

Benefit: At will, as a free action, you can empower the radiance surrounding you into a blazing glow that sheds bright light in a 10-foot radius (and shadowy illumination out to 20 feet). Undead within 10 feet of you take 1d4 points of damage per round they remain within your halo.

Rulebook: Book of Exalted Deeds (p. 44)

Edition: Supplementals (3.5)