Anthraxus

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.