The Spirit Realm

Kill last depleted before it regens. They got a ton of hp, so might as well just beat it down while you can. If you leave it alone, it'll just add when you do part 2

Just be careful that the last depelted is all you get. Sometimes Kess spawns before you can grab it and if you're not careful will aggro. We had Kess add when the puller tried to take them away from the raid, but a healer in his group auto-healed him without realizing what had happened. Everybody was oom at the end, but we ecked it out.

Not sure if he uses some kind of trick, but one of our RLs just runs up and tosses a shuriken and seems to get him alone with no issues. He pulls him toward the path where you came in, then turns and brings it to raid.

that's the trick occam