Head to 'The Founts' area on Dreadnaught patrol, and you will come to a room with a large chained mechanism in it. At the back of this area, is a large door, guarded by 3 'Warden's Knights' each with a different elemental shield. To open the door and get to Ecthar, you need to kill all 3 Knights outside the door with 1 super. I shocklocked them all and the door opened instantly with no dialogue. Ecthar can only be damaged by your sword Hope this helps ! Stolen from Reddit. You actually don't have to kill them all at once, but in a short period of time.