In A Sword Reforged quest line (the Exotic Sword quest) is a step called Blade of Night. In this step you have to find an enemy named Ecthar, The Sword of Oryx, and kill him. To get to him you have to go to The Founts area on the Dreadnaught and kill three Warden Knights that are guarding the door to The Asylum.
There is a special way in which they must be killed for the door to open. You have to kill all three of them in under 10 seconds, so first kill all the enemies in the room with the Warden Knights, then take each of the Warden Knights health down very low, but don’t kill them just yet. When all three of the Warden Knights health are low activate your super and kill them all as quick as possible. I’m talking within seconds of each other, after they are dead the door will unlock and open. If you fail to open the door, just leave The Founts area and come back and they will respawn.
Once you open the door, proceed ahead and you will see Ecthar surrounded by a bunch of enemies. Kill all the enemies first to make the Ecthar fight easy on yourself. Use your sword to kill Ecthar, but be careful, if you take damage just jump up on one of the many pillars and let your health recharge and then go attack him again. In this step my brother and I were both on the Ecthar step so he helped me kill him and we both got credit for the kill. So your friends can help just in case.