History of Aegis

The Aegis is the relic shield used in Iconoclasm, the Final Shape mission against The Witness. It is picked up from side rooms (left in phase one, right in phase two, per PCGamesN) and is used to break enemy shields such as Lenurae's and Dolgith's, and to guard against the arena-wide attack by standing over bright cracks of Light on the ground (GamePressure). Sources differ on whether breaking shields uses an "Aegis Super" (GamesRadar snippet) or alternate fire (PCGamesN); verify in game.