Their parents are the sea deities Keto and Phorcys. The Gray Sisters and Echidna are their other sisters. Medusa was a fair maiden and a priestess of the goddess of Athena, which meant that she couldn't marry in order to devote all her energy to the goddess. When in the temple of Athena, Poseidon came down from Olympus and took notice of Medusa, who became her lover. Poseidon took Medusa to one of Athena's most sacred temples on a date. Stheno and Euryale helped their younger sister to enter the temple. However, Athena caught the couple in her most sacred temple and found out that Medusa was no longer a virgin. Knowing that she could not take anger upon a god directly, Athena directed her wrath towards Medusa and cursed her without warning, to forever become a monster with slithering serpents as hair and a gaze that could turn a man to stone. Her sisters, Stheno and Euryale, were turned into Gorgons as well for assisting their sister into the goddess' sacred temple. Eventually, Medusa started to create statues because she felt lonely after her sisters faded away.
Spoils of War
Contrary to popular belief, only Medusa could turn people into stone by looking into people's eyes. She was killed by Perseus by cutting off her head, which he later used by Perseus to kill the sea monster Keto. Though their body parts weren't used as spoils of war; Stheno and Euryale leave behind vials of their blood instead. Athena received Medusa's head as a sacrifice from Perseus. She gave the head as a gift to her father Zeus, who used it to create his shield, Aegis, on oracular advise to win against the remaining Titans. He used the Aegis to defeat Aex (or Aix), who had a head as terrifying as her body was beautiful. Thalia Grace has a shield modeled after the Aegis, which usually causes enemies to be paralyzed or run away in terror.
Posing as a middle eastern lady named Aunty Em, Medusa tries to turn Percy Jackson, Annabeth Chase, and Grover Underwood into stone upon stumbling across her lair. Grover is the first to figure out that Medusa, not "Aunty Em," is their hostess. He sees a statue that looks unusually like his deceased Uncle Ferdinand and recalls that his Uncle Ferdinand was turned to stone by the monster Medusa.
Medusa holds a grudge against Annabeth because she is the daughter of Athena, the one responsible for Medusa's misery. Eventually, her head was chopped off by Percy Jackson just as the original Perseus. Her head was later used by Sally Jackson to turn her ex-husband Gabe Ugliano into stone. Later, Sally sells Gabe's statue to a museum.
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 Jackson was chased by Medusa's two sisters, Euryale and Stheno. He ran into them at a Bargain Mart, where the two were acting as store employees so they could find demigods that entered. Because he killed Medusa years ago (even though he couldn't remember it), the two seek revenge against him as their sister is still reforming in Tartarus. The two gorgons kept reforming after Percy had killed them numerous times, including hitting them with a cop car and smashing them with bowling balls. Stheno ignorantly tells Percy about gorgon blood, explaining that blood taken from the left side of their body would be deadly while blood from the right side could heal. They also inform him about an army heading south that will attack Camp Jupiter, but also inform him that they were brought back using the Doors of Death by their patron, Gaea. When Percy tried to call a truce by saying they couldn't kill each other (as they constantly reform and Percy's skin was like iron), they explain that he could be killed, even with the Achilles Curse, but it would simply by a matter of time before finding his Achilles heel. After escaping the two by sledding down a hill and carrying Juno to the borders of Camp Jupiter, he drowns them both in the Tiber River after they try to kill Frank, but they reform at some point afterwards and are at Camp Jupiter with Polybotes preparing to attack. Both are latter seen in aerial combat with the Eagles, defeating them. However they were both killed when the Camps reinforcements arrived, one of them being eaten by Mrs. O'Leary, although it is unknown which one.
Medusa is the youngest and most famous gorgon. She is the only one with the power to turn her victims into stone, being the envy of Euryale. Medusa used to be most beautiful as well, which is the reason Poseidon noticed her. Medusa is the only gorgon that has appeared in the first series. Her head was severed by Percy in The Lightning Thief, with the help of Grover and Annabeth.
Euryale is the middle among her gorgon sister. She is smarter than Stheno.
Euryale had faded along with the third sister, but was revived by Gaea. In The Son of Neptune, it is revealed that like Medea, Midas and Lycaon, she and Stheno are released from the Doors of Death and could reform within two hours.
Stheno is the oldest and the most vicious of the Gorgon sisters. She is rather naive as well. Sthena had faded with Euryale, but was revived by Gaea. The two are released from the Doors of Death. She blurted out gorgon facts to Percy and seems to have acquired a love for her cover-up job at the Bargain Mart.
- Petrification: Medusa possesses a gaze so terrible, it can turn anyone to stone. It only works if they look directly into her eyes.
- Charmspeak: Medusa has the ability to persuade people to open their eyes with a soothing voice.
- Gorgon Blood: Blood from their right side can cure anything, but the blood from their left side is deadly.
- Control of Animals (limited): The Gorgons have living, venomous snakes for hair.
- All three of the Gorgons are currently in Tartarus.
- The Gorgons are not listed to have any other power, but in some myths they are said to have unbreakable bronze and silver wings, teeth of gold, and Euryale had death-bellowing screams.
- In some myths, the Gorgons were beautiful maidens with brass wings like angels.
- All three of the Gorgons appear in the The Lightning Thief video game, but Stheno and Euryale are stuck in the Underworld.