From Citizendium, the Citizens' Compendium
Orpheus : From Greek mythology, he was (arguably) the greatest bard of all time who tried to sing for the release of his wife, Eurydice, who died and was in the underworld presided over by the god Hades. Hades and Persephone agreed to release his wife Eurydice from Tartaros (the underworld) to Orpheus on the condition that Orpheus was not to look back at her until they had both reached the upper world where humans lived. He peeked too soon; she vanished back into Tartaros, according to Elizabeth Vandiver, Classics scholar and authority on Greek mythology and Greek tragedy including the Iliad, Odyssey, Aeneid, Homer, and Virgil. This definition is based on her course Classical Mythology from The Teaching Company.