Dispater has no lair in vanilla NetHack. A spellcasting monster may summon him in Gehennom with the summon nasties spell, or a lawful demon (usually a prince; Asmodeus, Baalzebub, or Geryon) can gate him in.
He will not generally use his spellcasting attacks before he uses up his relatively harmless wand of striking. Therefore it is a very good idea to kill him as quickly as possible.
NetHack's incarnation of Dispater is based on the unique archdevil of the same name found in Dungeons & Dragons source books. The "City of Dis" mentioned in the Encyclopedia entry does not appear in NetHack itself, although some variants add a lair inspired by it.
In the source material as well as in NetHack, Dispater's apperance is that of a handsome human about 2 meters (ca. 7 feet) tall. Unlike his NetHack incarnation, the D&D Dispater also has two small horns, a tail and a cloven left hoof.
In the real world, Dīs Pater was a Roman god of the underworld, later subsumed by Pluto or Hades (Hades was Greek). Originally a chthonic god of riches, fertile agricultural land, and underground mineral wealth, he was later commonly equated with the Roman deities Pluto and Orcus, becoming an underworld deity.
The Roman ruler of the underworld and fortune, similar to the
Greek Hades. Every hundred years, the Ludi Tarentini were
celebrated in his honor. The Gauls regarded Dis Pater as
their ancestor. The name is a contraction of the Latin Dives,
"the wealthy", Dives Pater, "the wealthy father", or "Fater
Wealth". It refers to the wealth of precious stone below the