This is Mithraya, the final boss in the Trial of the Spheres. I’m not certain, when Celestia actually goes live, that the Trial of the Spheres will turn out to be the ultimate dungeon in the world, but it IS the one that drops all the level 58+ legendary armor. Putting traps on Mithraya is pointless; she just removes them.
I’ve heard again and again that Celestia is very difficult. I heard on Twitter that some are pronouncing the short deck dead in Celestia. That is wrong on both counts. We fought Mithraya with three wizards — a level 50 life wizard, a level 50 balance wizard, and a level 58 (and again at 60) fire wizard. There was never any doubt that we would win. Sure, the bosses in the Trials CHEAT — all Celestia bosses do. Sure, they start out with six power pips. But they don’t pump out the damage the way the bosses in Briskbreeze or the Warehouse do.