 According to an oracle, Iolcus would never prosper unless his ghost was taken back in a ship, together with the golden ram's fleece.This fleece now hung from a tree in the grove of the Colchian Ares, guarded night and day by a dragon that never slept.Pelias swore before Zeus that he would give up the throne at Jason's return while expecting that Jason's attempt to steal the Golden Fleece would be a fatal enterprise.