Anthraxus
From Marillia
Anthraxus, also known as Phraxas, is an ultroloth who currently holds the position of urgaloth—the (nominal) leader of the yugoloth race. He is one of the mightiest yugoloths in history.
He's a bit of a baller. He is the longest-serving urgaloth. He was briefly supplanted by Mydianchlarus, but Anthraxus returned and fucked him up real good.
Power Ranking
As far as I'm aware, Anthraxus has no official stats in D&D.
... However, there is a figure in Pathfinder known as the Oinodaemon, who may or may not be Anthraxus. He's sitting at a monstrous CR 37.