The legend of Médousa (Μέδουσα) is one of the hardest myths to deal with out of ancient Hellenic mythology. It tells the story of a beautiful woman, who got raped by Poseidon, and gets transformed into a hideous monster who can turn people to stone just by looking at them, by Athena, because of it. She spends the rest of her life trapped on an island, in isolation, while brave warriors try to kill her for her head, which will still turn people to stone once cut off. Perseus eventually does so and gives the head to Athena to place on her shield. The circle is complete and Médousa is dead, after a lifetime of horror which was not her fault to begin with.
It's one of the best known Hellenic myths, and the movies, series, books, comics and other mediums which feature it--or Médousa--are endless. Percy Jackson comes to mind, and Clash of the Titans, but there are many others. What's less well known is that this particular myth doesn't date back to ancient Hellas, but ancient Rome: it was
written by the Roman poet Ovid, in 8 B.C., in his
Metamorphosis.
"...He [Perseus] told of his long journeys, of dangers that were not imaginary ones, what seas and lands he had seen below from his high flight, and what stars he had brushed against with beating wings. He still finished speaking before they wished. Next one of the many princes asked why Medusa, alone among her sisters, had snakes twining in her hair. The guest replied ‘Since what you ask is worth the telling, hear the answer to your question. She was once most beautiful, and the jealous aspiration of many suitors. Of all her beauties none was more admired than her hair: I came across a man who recalled having seen her. They say that Neptune, lord of the seas, violated her in the temple of Minerva. Jupiter’s daughter turned away, and hid her chaste eyes behind her aegis. So that it might not go unpunished, she changed the Gorgon’s hair to foul snakes. And now, to terrify her enemies, numbing them with fear, the goddess wears the snakes, that she created, as a breastplate.’"