I don’t know if anyone ever outright stated this, but I know it was widely speculated on when he first popped up.
I mean, death god in the underworld. Makes deals for souls. Sketchy. Sounds exactly like Raid Finder Satan. That he was also charming as all heck both detracts and confirms this line of thinking.
Heck, I know a few people were disappointed when his sketch talk to dead Horde players in GYs turned out to be all a bunch of not-foreshadowing, and he’s just kinda a fun guy instead.