The Greek mythology of Jason and the Golden Fleece has more than one version. What follows is a brief description of one such tale.
Jason was not a god himself, but the son of a king. His father was dethroned by his own brother and this put Jason out of line for the kingship. Jason was sent away on an impossible task by the then king, Pelias, to retrieve the fleece in a faraway and dangerous land. Jason was promised by Pelias that he would give up the throne if Jason brought him the fleece.
Jason decided to enlist some help and he assembled a dream team of warriors and demi-gods (an ancient version of the avengers or justice league). They set out to sea and had many stops along the way. They fought battles and fell in love. Once they reached the land of Colchis, where the fleece was residing, their journey was not over.
The King of Colchis, Aeetes, gave Jason and his team, called the Argonauts, three tasks before allowing him to obtain the fleece. The first task was to yoke a team of fire-breathing oxen and plow a field, the second was to sow the teeth of a dragon in a field and then fight the warlike men that grew from the field, and the third and last task was to slay the sleepless dragon that guarded the fleece.
Jason succeeded in all three tasks and eventually obtained the golden fleece. It was allegedly made from a golden ram. He returned to his realm and took his rightful place as king.