Attach to a hero with Sentinel. Limit 1 per hero.

Response: Exhaust Raven-winged Helm to prevent 1 point of damage just dealt to attached character.

He had a small hauberk, its rings of forged of steel, maybe, yet black as jet; and a high-crowned helm with small raven-wings on either side, set with a silver star in the centre of the circlet.
–The Return of the King