In Crushbone: The top orc himself. Emperor Crush is found in the castle in Crushbone.
In Crushbone (Level 90 Revamp): Emperor Crush is found in the watch tower of the castle. He doesn't summon and is rootable/snareable.
In Crushbone (Demise of the Emperor): Part of the "Demise of the Emperor mini-raid.
In Al'Kabor's Nightmare: Slowable; placeholders are "the Crushbone strategists on Faydark island".