Gorgon

Gorgons (Ancient Greek: ┌οργονς) were terrifying monsters that were turned into snake women by the goddess Athena after Medusa had an affair with Poseidon in one of her sacred temples.

Description
Contrary to popular belief, only Medusa could turn people into stone by looking into people's eyes. They were three monstrous sea spirits whose names were Stheno, Euryale, and the only mortal among the three, Medusa. Medusa was killed by Perseus by cutting off her head. Her head was later used by Perseus to kill the sea monster, Keto. Zeus created his shield, Aegis, on oracular advise so he could win the war against the Titans. He defeated the gorgon Aex (or Aix), who was either the daughter of Helios (with a head as terrifying as her body was beautiful) or alternatively the son of Typhon and Echidna. He used the skin of a goat and fixed upon it the head of the gorgon Aex. It was said Zeus gave Aegis to his daughter Athena once the war was over.

Becoming Gorgons
In the beginning, Medusa, a fair maiden was a priestess of the goddess of Athena. This meant that she could not marry so she could devote all her energy to Athena. When in the temple of Athena, Posedion had come down form Olympus and appeared in the temple, Medusa was no longer a virgin and was outcasted from ever becoming a priestess of Athena. Athena knowing that she could not take anger upon a god directed her wrath towards Medusa. Athena became outraged that this event had happened in her temple and curse Medusa without warning, to forever become the first Gorgon. Medusa and her two sisters, Stheno and Euryale, were turned into the three Gorgons by Athena. The transformation was a punishment. 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' sacred temple and because they were kind enough to share their sister's fate. It is said that Medusa created statues because her sisters faded away and she was left lonely. In some myths, the Gorgons were beautiful maidens with brass wings like angels.

The Lightning Thief
Medusa tries to turn Percy, Annabeth, and Grover 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 Uncle Ferdinad, 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. However, Medusa told them that her sisters had faded and now she was alone. Eventually her head was chopped off by Percy Jackson as a reference to the original Perseus, and was used by Sally Jackson to turn her ex-husband Gabe into stone.

The Lost Hero
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.

The Son of Neptune
Upon leaving the Wolf House, Percy Jackson was chased by Medusa's two sisters, Euryale and Stheno (who Percy originally thought was named Beano). 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 can'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's 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 aireal combat with the Eagles, deafing 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
Medusa is the only gorgon that has appeared in the first series, her head was severed by Percy Jackson 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, and 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. Her parents were Ceto and Phorcys. The Graiae are her other sisters besides Stheno and Euryale.

Euryale
The immortal sister of Medusa. She has been known for bellowing cries. She had faded, along with the third sister but was revived by Gaea.

It was said that Euryale was the middle among the her sisters. In The Son of Neptune, it is revealed that like Medea, Midas and Lycaon, Stheno, and she is released from the Doors of Death and could reform within two hours. She is the smarter of the two.

Stheno
The immortal sister of Medusa. She is remembered as the most vicious of the Gorgon sisters. She had faded with Euryale but was revived by Gaea. Stheno was said to be the eldest of her sisters.

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 cover-up job at the Bargain Mart. She appears in The Son of Neptune.

Abilities

 * They have living, venomous snakes for hair.
 * Blood from their right side can cure anything, but the blood from their left side is deadly.
 * Medusa possesses a gaze so terrible, it can turn anyone to stone. It only works if they look directly into her eyes.
 * They have the ability to persuade people to open their eyes with a soothing voice, though only Medusa has been shown to do this.

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.

Aegis
Aegis is a bronze shield that Athena gave to Zeus that has an imprinting of Medusa, one of the Gorgons, on it. Thalia Grace has a shield modeled after it which usually causes enemies to be paralyzed or run away in terror.

Trivia

 * All three of the Gorgons appear in the The Lightning Thief (video game), but Stheno and Euryale are stuck in the Underworld.
 * All three of the Gorgons are currently in Tartarus.