So, Perseus was a hero, beloved of the Moon Goddess, Athena, and Medusa was an evil monster, right?
Not hardly.
In fact Medusa was a victim, Perseus a simple dupe, and Athena vengeful and manipulative.
Medusa may be one of the most misunderstood characters in all of Classical Mythology. Typically, she is seen as nothing more than someone who is hideous to look upon, and perhaps as someone who has a grudge against men. But when her story is truly looked at, and the reasons for her monstrous appearance are seen, her plight becomes much more sympathetic.
The snakes that she has for hair, and her ability to turn anyone who looks her in the eye to stone is probably the things that are most associated with her. And fans of the film Clash of the Titans (the original, and perhaps the remake as well) will probably know this feature of hers all too well. But how did she come to this state?
Originally, she was very beautiful, and she had many suitors. One day Poseidon, the god of the seas, came upon her, worshiping in one of Athena's temples (where she was a priestess). Seeing how beautiful she was, and wanting her, he decided that he was going to rape her inside Athena's temple.
Once Athena found out what had happened, she was furious - not for the rape of an innocent mortal woman, but for the the desecration of her temple . . . And since Athena could do nothing to her uncle, such a powerful and influential god in his own right, she decided that she would take her anger out on Medusa instead. That is when Medusa became the monster that we think her to be, the woman with the snakes for hair, and the stony gaze. So, not only was she the victim from Poseidon's unwanted advances, she was again the victim when she was punished by Athena for Poseidon's actions (by having to spend the rest of her life alone).