I have just gotten the quest, Aberrus. The Shadowed Crucibl: Sarkareth.
slay Sarkareth. I do not see Sarkareth as a boss in the raid
If you’re trying to find him in raid finder, he won’t be active until the week of June 19th. If you want to kill him before then, you’ll need to do the raid on Normal, Heroic, or Mythic difficulty.
ok thank you . I have done the raid, he was not there. thanks for the help I’ll wait until the 19th