i’m pretty certain that he only spawns when you kill the bosses before barlok or whatever its name is (the bridge guardian). i have been in there quite a few times (for the Rag mount) and i’ve always had to clear the bosses before mojordomo for him to fight you.
if anything i know balrok and alysrazor will be mandatory, since he has dialogue with them…but still not sure if you can skip any of the others.
it’s a fairly common drop, so if you do have to full clear, it’s not something you’ll have to do over a long period of time. hope that helps, and gl with the fire kitten!
i love that skin a lot, because it has an ambient fire crackling sound whenever you’re in cat form (which is unique)…i wish it had more of a blazing trail that follows you when you run though (Similar to the treant form when you catch embers from nearby fires & they leave a smoky trail when you run)