Orcus in the context of Roman mythology

Hades (/ˈheɪdiːz/; Ancient Greek: ᾍδης, romanized: Hā́idēs, Attic Greek: [háːi̯dεːs], later [háːdeːs]), in the ancient Greek religion and mythology, is the god of the dead and riches and the King of the underworld, with which his name became synonymous. Hades was the eldest son of Cronus and Rhea, although this also made him the last son to be regurgitated by his father. He and his brothers, Zeus and Poseidon, defeated, overthrew, and replaced their father's generation of gods, the Titans, and claimed joint sovereignty over the cosmos. Hades received the underworld, Zeus the sky, and Poseidon the sea, with the solid earth, which was long the domain of Gaia, available to all three concurrently. In artistic depictions, Hades is typically portrayed holding a bidentand wearing his helm with Cerberus, the three-headed guard-dog of the underworld, standing at his side.

Roman-era mythographers eventually equated the Etruscan god Aita,and the Roman gods Dis Pater and Orcus, with Hades, and merged all these figures into Pluto, a Latinisation of Plouton (Ancient Greek: Πλούτων, romanized: Ploútōn), itself a euphemistic title (meaning "the rich one") often given to Hades.

In ancient Roman religion and mythology, Pluto (Ancient Greek: Πλούτων, romanized: Ploútōn, Latin: Plūto or Plūton), also known as Dis Pater or Orcus, was the god of the dead and the king of the underworld. The name was originally an epithet or theonym for Hades in ancient Greek religion and mythology, although Pluto was more associated with wealth and never used as a synonym for the underworld itself, representing a more positive concept of the god who presides over the afterlife. He was the eldest son of Saturn (Cronus) and Ops (Rhea), as well as the brother of Jupiter (Zeus) and Neptune (Poseidon). Pluto later married Proserpina (Persephone) and shared many of Hades' attributes, such as the bident, the cap of invisibility, and the three-headed guard dog Cerberus.

While Pluto is commonly considered the Roman equivalent of Hades, the name Plouton was already used by the Greeks to designate Hades and was later adopted by the Romans for their god of the underworld, Dis Pater, which often means "Rich Father" and is perhaps a direct translation of Plouton. Pluto was also identified with the obscure god Orcus, name that the Romans adopted from the Etruscans and which, like Hades, was both for the god of the underworld and for the underworld as a place. On the other hand, Ploutōn was frequently conflated with Ploûtos, the Greek god of wealth, because mineral wealth was found underground and because, as a chthonic god, Pluto ruled the deep earth that contained the seeds needed for a bountiful harvest.

Orcus (minor-planet designation: 90482 Orcus) is a dwarf planet located in the Kuiper belt, with one large moon, Vanth. It has an estimated diameter of 870 to 960 km (540 to 600 mi), comparable to the Inner Solar System dwarf planet Ceres. The surface of Orcus is relatively bright with albedo reaching 23 percent, neutral in color, and rich in water ice. The ice is predominantly in crystalline form, which may be related to past cryovolcanic activity. Other compounds like methane or ammonia may also be present on its surface. Orcus was discovered by American astronomers Michael Brown, Chad Trujillo, and David Rabinowitz on 17 February 2004.

Orcus is a plutino, a trans-Neptunian object that is locked in a 2:3 orbital resonance with the ice giant Neptune, making two revolutions around the Sun to every three of Neptune's. This is much like Pluto, except that the phase of Orcus's orbit is opposite to Pluto's: Orcus is at aphelion (most recently in 2019) around when Pluto is at perihelion (most recently in 1989) and vice versa. Orcus is the second-largest known plutino, after Pluto itself. The perihelion of Orcus's orbit is around 120° from that of Pluto, while the eccentricities and inclinations are similar. Because of these similarities and contrasts, along with its large moon Vanth that can be compared to Pluto's large moon Charon, Orcus has been dubbed the "anti-Pluto". This was a major consideration in selecting its name, as the deity Orcus was the Roman/Etruscan equivalent of the Roman/Greek Pluto.