The term 'Underworld God' refers to a group of deities from ancient mythology who were associated with the afterlife and the underworld. These gods include PLUTO (5 letters), DIS (3 letters), HADES (5 letters), Osiris (6 letters) and ORCUS (5 letters). PLUTO was the Roman god of the underworld, while DIS was the Etruscan equivalent. HADES was the Greek god of the underworld, and Osiris was the Egyptian god of the afterlife. ORCUS was an Etruscan and Roman god of the underworld.