Jason was a little-known hero who, in order to win the throne of Iolcus (in Thessaly), recruited a mighty crew and set sail in the Argo in search of the Golden Fleece. They found it only with the assistance of the goddess Hera and the princess Medea, who betrayed her father and eloped with Jason and the Fleece. Jason made it safely home, claimed the throne and married Medea. This did not end well for either of them.
Jason’s crew was a who’s who of Ancient Greek heroes. It included Hercules, Theseus, Castor, Pollux, Laertes (father of Ulysses), Bellerophon, Iolaus, Nestor, Orpheus, Deucalion, Asclepius, Atalanta, Peleus (father of Achilles) and Autolycus. In fact, not counting the heroes of the Trojan War (who were mostly not yet born at this point), the only significant Greek hero not to participate was Oedipus.