Orcus

Orcus is the demon lord of undeath. One of the most powerful demons in the Abyss, Orcus seeks total control over death and undeath alike; as a result, he was a long-time nemesis of both Nerull and Wee Jas. With their deaths during the Deity War, Orcus has set his sights on the Raven Queen, the only being who now stands between him and complete dominion over death.