If you activate the shield relic on the central platform and begin shooting Atheon, you somehow destroy some key that would unlock the "Vault of Glass".
When fighting Atheon, once three members of the raid team are teleported to either Venus or Mars, have two of the team members open the vex warpgate for the appropriate area to allow the teleported players to rejoin you in your fight, and have the remaining player kite or lure Atheon up the stairs and towards the large doorway behind where he originally spawns.
Once he is up there and the teleported players have returned through the warpgate, have the player who holds the shield relic run all the way up and behind Atheon and shoot him in the back with the shield super, while Atheon has his back turned.
Optionally, a titan can lure Atheon underneath or closer to the doorway by using his/her bubble shield super.
While all of this is going on the other members should be killing whatever other enemies are spawning.
Rinse and repeat until "something happens"?
(Shooting Atheon apparently disallows this to be completed, so don't do it.)