Medusa and her sisters Euryale and Stheno were the Gogons, the three daughters of Phorcys and Ceto. They lived in the far West. Their heads were were entwined with snakes and their necks protected by dragons' scales. They had hands of bronze, and their gaze was so penetrating that anyone who encountered it was turned to stone. Poseidon alone was not afraid of them, for he had coupled with Medusa and fathered a child by her. But because Poseidon had taken Medusa in the Temple of Athena, Athena had punished her by changing her beautiful hair into live snakes.

Perseus cleverly slew Medusa by taking his aim upon her by looking at her reflection in his gleaming shield. When he severed her head, from her neck sprung the winged horse Pegasus and the warrior Chrysaor, born brandishing a golden sword. Perseus put the severed head of Medusa into his shoulder bag to use as a weapon and set out for home. Euryale and Stheno pursued him, but he wore the helmet of Hades which rendered him invisible.