Invoker’s Aura

Epic Tier
Prerequisite: 21st level, invoker
Benefit: Until the end of your next turn, after you use a Channel Divinity power, any enemy within 2 squares of you that hits you or any enemy that ends its turn within 2 squares of you takes radiant damage equal to 5 + your Wisdom modifier. No enemy can take this damage more than once per turn.

Published in Divine Power, page(s) 141.