I was in a game a long time ago were the villain had an amulet or a set of bracers ( i believe they were a relic ) that reflected damage back to attacker. Made life hell for our cleric do to the fact this was prior to aoe channeling. I don't believe that it was home made because i remember looking at it in a book but for the life of me i cant remember what book or the name of the item.
I believe you speak of the Amulet of Retribution from Book of Exalted Deeds that returned half the damage dealt to the Attacker and half the damage to the user
Though I imagine it's not what you are thinking of there's also a spell seed in the Epic Level Handbook (Seed: Reflect) which could be used as the basis for an Epic Spell/Artifact/Relic doing this sort of thing.
