|Religion in NetHack
Orcus was the god of the Estrucan and later Roman underworld, and a deity that punished broken oaths. As with Hades, Orcus's name was also used for the underworld itself; in later Roman tradition he was conflated with Dis Pater, who inspired the Dispater of Dungeons & Dragons.
Like many other deities associated with death and the underworld, his name was used for demons and other underworld beings, including the Orcus of Dungeons & Dragons that NetHack players are more familiar with. According to a side-note in one of Tolkien's manuscripts published by his son Christopher, as well as an unpublished letter to Gene Wolfe, Orcus was believed to be the root of the older Anglo-Saxon term "orc", meaning demon - a notion Tolkien expressed skepticism towards in the latter source.