Orcus, the prince of undeath, excerpted from the Monster Manual.
Orcus, Prince of the Undead, is one of the most powerful demons in the Abyss. He is also known as Prince of Undeath and the Blood Lord.
Orcus is described as a foul and corpulent humanoid, with goat legs, large bat-like wings and a ram's head. He wields a large skull-capped mace called the Wand of Orcus.
He is the ruler of Thanatos, the 113th Layer of the Abyss, a dark realm of graveyards, necropolises and mausoleums, with legions of the undead wandering the dark, foggy streets and dead forests, under the shadow of his towering citadel.
Those that follow Orcus are usually powerful undead such as vampires and liches, as well as necromancers. His greatest follower and exarch is Doresain, the Ghoul King.
Like all demons, Orcus seeks destruction. However, he is focused on the Raven Queen, goddess of death, fate and winter. Orcus and his followers seek to overthrow the Raven Queen, allowing the Prince of the Undead to usurp her throne, conquer the Shadowfell, and take command of death and the souls of the dead. For this reason, the Raven Queen and her followers oppose him. Vecna is interested in their battle, and has worked against Orcus as he prefers the Raven Queen as the god of death, though he too desires the power. The hatred between Orcus and Demogorgon, Prince of Demons, is legendary. Orcus is a contender to the title, but is no match for Demogorgon.