Medusa was a beautiful priestess of Athena. Her beauty even got the attention of Poseidon. One day while in the temple of Athena(On the Acropolis) Poseidon appeared before her, grabbed her and raped her in the temple of Athena. The next day, Medusa was with her sisters Stheno and Euryale, but then Athena appeared before them in both rage and pity, Athena cursed Medusa to be a Gorgon so it would never happen again, Medusa's sisters were caught in the crossfire of the curse and also got transformed into Gorgons.