King Pelias, warned by an oracle that a man with one sandal would cause him to lose the throne, was alarmed when he saw Jason because, while crossing a river, Jason had lost one of his sandals. To stave off the oracle's predicted ill fortune, Pelias sent Jason on what was presumed to be a suicide mission: to fetch the Golden Fleece from Colchis.
Jason succeeded in the seemingly impossible quest, with the help of his many heroic friends, known collectively as the Argonauts, and by charming the king's daughter Medea, a witch or sorceress. When he left Colchis, Jason was oligated to take Medea with him because she had betrayed her father. On their sea passage, Medea killed her younger brother and tossed his limbs upon the sea.
Medea won the throne of Iolchus for Jason by conniving to have Pelias' own daughters kill him.
The pair continued together and had two sons, but later Jason reconsidered marriage to such a barbarian princess, so he set her aside in order to marry a Corinthian princess, Glauce, daughter of King Creon.
Medea was enraged, caused the death of Glauce and Creon, and in vengeance against Jason, destroyed Jason's and her children.
Try the Jason and Medea Quiz
For more on Jason, see Jason's Angels