Here is again a video of how to properly fight Atheon, the final boss in the Vault of Glass. The Relic Holder should be right behind the last non-relic holder to exist the portal in order to maximize the time everyone has to use "Time's Vengeance". Then the relic holder should jump onto the center platform in the rear of the main chamber and hold the cleanse shield, this not only keeps everyone cleansed but also blocks any in coming fire from the ads AND Atheon itself.