Medusa, along with her sisters, Stheno and Euryale, were the Gorgon daughters of the sea Titans Porcys and Ceto.Medusa wasn't always hideous. There is a particular myth in which Medusa was originally a beautiful maiden with long silky hair that she was very proud of.
Once said to have been extremely wise they all served as priestesses to the virgin goddess of wisdom, Athena. However, the Seagod Poseidon desperately desired Medusa. In a moment of raw passion he raped Medusa inside of Athena's temple of worship. In anger, the three sisters became petty and vindictive toward men.
Appalled either by the sisters' pettiness, or by the sacrilegious sexual act, Athena transformed Medusa and her sisters (all of whom were now wicked) into hideous beasts with scaly skin, dragon's wings and hair formed of dozens of coiling snakes. As a result, all who beheld the Gorgons were instantly turned to stone when their eyes met.
Medusa and her sisters became even more vicious and took great pleasure in torturing their victims until the day when Perseus, with the help of Athena and Hermes. Using the winged sandals and Hades' helmet of invisibility provided by Hermes, and Athena's silver shield, Perseus approached the sleeping Medusa.
Perseus killed the monster by looking at her reflection on his shield, which prevented him turning into stone. He cut off her head and presented it to Athena, who placed it in the center of her Aegis, the protective shield which she wore over her breastplate.
But first, Perseus had to outrace Medusa's enraged sisters, who flew after him, the snakes on their heads and waists hissing at his heels. Perseus managed to escape thanks to the winged sandals of Hermes, and by wearing Hades' helmet of invisibility.
Upon her death, the seeds of the union of Poseidon & Medusa germinated into the young colt named Pegasus and the giant (or another winged horse) named Chrysoar, who sprang forth when the blood of Medusa made contact with the seafoam. Perseus married the princess Andromeda and they had a daughter whom they called Gorgophone (named for the slain gorgon). Medusa was also identified with the Libyan Queen and serpent-goddess of wisdom of the Amazons. Her name is derived from the Sanskrit medha, Greek metis, and Egyptian met or maat all meaning "wisdom."