Hermes' winged ram with gold fleece that was sent by Nephele to save Prince Phrixos from being sacrificed at the alter of Zeus. Phrixos and his sister, Helle, flew on the back of Chrysomallus in their escape.
Phrixos, after loosing his sister in a fall over Hellespont, landed alone on the land of Colchis where he sacrificed the ram in the name of Zeus. Zeus, impressed, made the constellation Aries in the sky.
Chrysomallus' Golden Fleece was sent by Phrixos to his father-in-law who kept it in the Sacred Grove of Ares to be guarded by a terrible sleepless dragon.
The Golden Fleece was, at a later point, central to the story in which Jason assembled and lead the Argonauts, setting out on a quest to retrieve it.