In the center of the rift that is the Eye of Regulos:
Blast your way in to the Pillars. You will have to kill a few Shademages to get in clean. Then pound the pillars and kill the 2 very weak Skeletons that show up from time to time. Once the Pillars are both down you are ready for the Altars. Each time you click the thingy floating above them a Lord and Lady of the Endless Court will arrive. Take them as they come.
When they are done the Shadow of Alsbeth appears. Naturally, you need to kill it. Best to fight it in the center to avoid adds as the Shademages should be respawning by now.