Medusa and her two sisters, Stheno and Euryale, were turned into the three Gorgons by Athena. The transformation was punishment; the human Medusa had been caught with Poseidon consorting in her temple. The result was a monstrous demon with slithering serpents as hair and a gaze that could turn a man to stone.
Medusa's sisters were turned into Gorgons as well for the act of assisting their sister into the goddess's sacred temple, and because they were kind enough to share their sisters fate.
In The Lightning Thief, it is said that Medusa created statues because her sisters faded and she was left lonely. In some myths, the Gorgons were beautiful maidens with brass wings like angels.
- Living, venomous snakes for hair
- Blood from their right side can cure anything, but the blood from their left side is deadly
- Gazes so terrible, it can turn anyone affected to stone (though, only Medusa has this ability)
- The ability to persuade people to open their eyes with a soothing voice
The Gorgons are not listed to have any other power, but in some myths they are said to have throats of unbreakable bronze and silver wings, teeth of gold, and tails that can wrap an elephant.
When Chiron is explaining how the use of technology can be dangerous for demigods, he says that a demigod once tried to Google the Gorgons, causing them to appear. It is not mentioned if one or all of them appeared.
Upon leaving the Wolf House, Percy is being chased by Medusa's two sisters, Euryale and Stheno (who Percy originally thought was named Beano), because he killed Medusa years ago (even though he can't remember it). The two gorgons keep reforming after Percy has killed them. Stheno ignorantly tells Percy about gorgon blood, with that taken from the left being deadly while from the right could heal. They also fill him in on some of the stuff readers learned in the previous book, such as Gaia, their patron opening the doors from Tartarus, and they also tell him he has the Achilles Curse, and he is the son of a sea god, which he apparently didn't know. He drowns them both in the Tiber after they try to kill Frank, but reform soon afterwards.
Medusa's head was severed by Percy in the Lightning Thief, with the help of Grover and Annabeth. It was said that Medusa was the youngest Gorgon among the three, as well as the most beautiful, which is the reason Poseidon noticed her. She is also the most famous. Medusa is also the only one with the power to turn her victims into stone, being the envy of Euryale.
In The Son of Neptune, it is revealed that she and Stheno are released from the doors of death and could reform within two hours. She is the smarter of the two.
The immortal sister of Medusa. She has been most remembered to be the most vicious of the Gorgon sisters. She has faded with the second sister. Stheno was said to be the eldest of her sisters.
In The Son of Neptune, Euryale and she are released from the doors of death. She is more naive as she blurts out gorgon facts to Percy and seems to have acquired a love for her job at Bargain Mart.