Half-Olympian son of Zeus by Dia, queen of the Lapiths. Inseparable friend of Theseus. Centauromachy at his wedding to Hippodamia is depicted on the Parthenon metopes. After Hippodamia's death, descended to Hades with Theseus to abduct Persephone; tricked by Hades into the Chair of Forgetfulness, where he remained imprisoned forever — Theseus was rescued by Heracles but Pirithous was not.