Pegasus was the son of Medusa and Poseidon, born when Perseus beheaded Medusa. Medusa was reputed to be very beautiful but angered Athena by having an affair with Poseidon. Athena then turned Medusa into a snake hair Gorgon.
Pegasus was known as a gentle, helpful creature who Zeus granted immortality by turning him into a constellation upon his death. Because of his ability to fly, Pegasus is often associated with divine inspiration.