Medusa, at least in some accounts, was once a beautiful woman who attracted the attention of
Poseidon. When the god chose to mate with her, he was in the temple of
Athena. Athena was furious and got revenge by turning Medusa into a monster so horrible that a single glance at her face would turn a man to stone. Even after Perseus, with Athena's help, separated Medusa from her head -- an act that allowed her unborn children, Pegasus and Chrysaor, to emerge from her body -- the head continued to exert its power.
The head of Medusa is often described as being covered with snakes instead of hair.
Medusa is one of the Gorgons, three daughters of Phorcus. Her sisters are the immortal Gorgons, Eryale and Stheno.