Aeëtes was born from the union of Helios, the sun god whose blazing chariot lights the world each dawn, and Perseis, one of the three thousand daughters of Oceanus and Tethys, the primordial deities of the sea. His sisters were Circe, who would later rule the island of Aeaea and turn Odysseus's men into swine with her magic, and Pasiphae, who would become queen of Crete and mother the Minotaur, the half-man half-bull monster that lurked in the Labyrinth of Knossos. Some say his mother was Asterope instead of Perseis, but all agree that Aeëtes carried the fire of his father in his blood. He ruled Colchis, a rich kingdom at the eastern end of the Black Sea where the River Phasis runs down from the Caucasus Mountains, a land of gold and magic that the Greeks regarded as the edge of the known world.

The fleece came to him through the flight of Phrixus, the son of King Athamas of Orchomenus, who had been saved from sacrifice by a golden-fleeced ram sent by the gods. The ram carried Phrixus and his sister Helle across the sea, but Helle fell into the strait that still bears her name, the Hellespont. Phrixus rode on alone to Colchis, where Aeëtes received him with honour and gave him his daughter Chalciope for a wife. In gratitude, Phrixus sacrificed the ram to Zeus and gave its wondrous fleece to the king. Aeëtes hung the golden hide in a grove sacred to Ares, the god of war, where a monstrous serpent - born in some accounts from the blood of the Titan Typhon - coiled around the oak and never closed its eyes. An oracle had spoken: Aeëtes would hold his throne only so long as the fleece remained in the grove. The king, knowing this, grew cruel and suspicious. He sacrificed any foreigners who came to his shores, hoping that tales of his brutality would keep wanderers away.

Aeëtes had children by more than one wife. By Idyia, a daughter of Oceanus, he had Medea and Chalciope. By another woman, some say Eurylyte or the Nereid Neaera, he had Apsyrtus. Medea was trained in the arts of sorcery by her aunt Circe and served the goddess Hecate, the queen of ghosts and witchcraft who walks the earth by night with her pack of hounds. Chalciope married Phrixus and bore him sons, who would one day return to Colchis as strangers themselves. Apsyrtus was a young prince, his father's hope for the future. The family was powerful, proud, and bound by prophecy to a treasure they could never safely keep.

When the Argo, the fifty-oared ship built by Athena and manned by the greatest heroes of Greece, reached the mouth of the Phasis, Aeëtes knew at once that the oracle's warning had come to pass. Jason, the one-sandalled heir of Iolcos who had been sent by the usurper Pelias on a quest meant to destroy him, came to the palace with Phrixus's sons and asked for the fleece. Aeëtes received them at his table but his heart was full of rage and fear. He suspected a plot to steal his throne, and he was not wrong: the gods themselves, Hera and Athena, had arranged this voyage to punish Pelias and to settle old scores. When Jason asked for the fleece, Aeëtes did not refuse outright. Instead he set three tasks, each one a death sentence dressed as a trial.

First, Jason must yoke two bulls that grazed on the plain of Ares, creatures with hooves of bronze and breath of fire, and drive them through a field to plough it. Second, he must sow the field with the teeth of a dragon that had once guarded a spring, teeth that would sprout into armed warriors who would rise up to kill the sower. Third, he must overcome the sleepless dragon that guarded the fleece itself. Aeëtes boasted that he performed these labours himself each day, yoking the bulls in the morning and cutting down the earthborn warriors by evening, though this was more threat than truth. He swore that if Jason succeeded, the fleece would be his, but privately he planned to burn the Argo and kill every man aboard.

What Aeëtes did not foresee was the treachery of his own daughter. The goddess Hera had persuaded Aphrodite to send her son Eros, the winged archer of love, to shoot Medea with an arrow of gold, and the princess fell helplessly in love with Jason. She gave him a magical ointment distilled from the blood of Prometheus, the Titan chained in the Caucasus for stealing fire from the gods, which made his body impervious to flame for a single day. With it he yoked the bulls and ploughed the field. When the earthborn warriors sprang from the dragon's teeth, Medea had already told him to throw a stone into their midst, and in the confusion they turned on each other and were destroyed. Finally, in the dark of night, Medea led Jason to the grove of Ares, where she sang the serpent to sleep with charms and herbs, and Jason lifted the Golden Fleece from the oak.

Aeëtes discovered the theft at dawn and flew into a fury that shook the palace. He called out his fleet and set off in pursuit of the Argo, determined to burn the ship and hang Jason's corpse from the mast. Medea, knowing her father's speed and cruelty, took her brother Apsyrtus - some say she lured him into a trap, others that she killed him on the ship itself - and cut his body into pieces. She threw the limbs and torso overboard one by one, and Aeëtes, compelled by grief and the need to give his son a proper burial, stopped at each splash to gather the pieces from the water. By the time he had collected what he could, the Argo had vanished into the mist. The Greeks call this the murder of Apsyrtus, and it was the first of the crimes that would stain Medea's name forever.

When Aeëtes returned to Colchis, he found that his brother Perses had seized the throne in his absence, for the oracle had spoken true: the loss of the fleece meant the loss of the kingdom. Aeëtes was deposed and driven into exile or imprisonment, his cruelty and suspicion having won him no friends among his own people. Years later, Medea herself returned to Colchis after being cast out by Jason and by Athens, and found her father in chains or in hiding. She killed Perses with poison or witchcraft and restored Aeëtes to his throne, a final act of daughterly devotion that could never undo what had been done. What became of Aeëtes after this restoration, the old stories do not say. He may have died in his bed, or he may have passed into legend as one more king whose doom was written in gold and guarded by a serpent that could not sleep.