Orcus

Orcus is the demon lord of death and one of the most fearsome powers of the Abyss. He is a powerful, insane, and cruel god of the undead who rules over the hordes of the dead and demons.
Orcus is often depicted as a gigantic demon with a horned head and a powerful staff, possessing the ability to resurrect the dead and make them his servants. He is a bitter enemy of all divine forces of life, as his only goal is the annihilation of all living beings to flood the world with an army of the undead.
Orcus is inspired by several mythological and folklorical narratives. In Roman mythology, there exists a figure named Orcus, who was originally the god of the underworld. He was often associated with the lesser-known aspects of the underworld, such as punishing sinners and ruling over the souls of the deceased.
In ancient Rome, Orcus was regarded as a dark deity, particularly known as a god of vengeance. He was responsible for punishing the deceased who had violated moral norms.
In medieval folklore and demonology, Orcus is often described as a demonic entity that rules in the hells or the underworld and is worshiped by the magical powers of wizards and witches who create undead.
The staff of Orcus is one of the most powerful artifacts in the multiverse of Dungeons & Dragons. If one brings it into their possession and manages to use it without dying, it grants unimaginable power. What exactly it can do and which other particularly powerful artifacts you should acquire if you have the chance, you can read here: Dungeons & Dragons: The 5 most powerful artifacts you definitely want to get your hands on