The Golden Fleece is a mystical artifact that has the ability to heal any mortal it is placed on. The Argonauts retrieved the Fleece to save King Aeson's life (Young Hercules).
Ten years later, on the anniversary of the Argonauts bringing the Fleece to Argos, it was stolen by Castor and the Blood-Eye Cult. They took it to an island and a second a expedition of the Argo was launched to retrieve it (HTLJ "Once a Hero").
Gallery[]
In Argos in "Once a Hero"
Castor with the Fleece in "Once a Hero"