Legend of the Gorgon Monster
The trio received their nicknames due to their supposed heroic act of slaying a monster called the Gorgon (ゴルゴン Gorugon?). As punishment, the Gorgon cursed the three of sisters with a pair of eyes on each of their backs, which would petrify anyone who set eyes on them. Also, as part of the curse, Hancock has the ability to petrify anyone that shows lust to her, while Sandersonia and Marigold can transform into human-snake hybrids at will. As such, whenever the three sisters bathe, the rest of the tribe must evacuate the main castle, and set up barriers around the area, to prevent petrification. However, due to their deed, the Gorgon Sisters were praised as heroines of the entire Kuja tribe, and became enormously popular.
In truth, what the three sisters bear on their back is the "Hoof of the Flying Dragon" (天駆ける竜の蹄 Ama Kakeru Ryū no Hizume?, FUNimation subs translate this as the Claw of the Celestial Dragons), which is a symbol of them being slaves to the World Nobles. It is burned deep into their flesh so it will forever show that they are less than humans. Their powers from their "curse" that they received from the Gorgon were actually Devil Fruits fed to them as a form of cruel entertainment for their masters.
For four years, the sisters were abused and humiliated day and night, wishing for death. Like many people, slaves or not, they did not dare defy the World Nobles, for the fear of facing a Marine Admiral. Then, when Fisher Tiger attacked Mary Geoise and freed every slave there, the Gorgon Sisters owed him a debt which they could never repay.
Even after being liberated, the sisters were unable to return home, until they met Elder Nyon, former empress of the Kuja tribe, as well as Silvers Rayleigh and Shakuyaku. In order to hide their shameful past to the rest of the tribe, they used the Kuja's lack of knowledge about the outside world (especially about Devil Fruits) and concocted a story about the Gorgon. As such, when any of the three sisters were to take a bath, the rest of the tribe were to evacuate the area, in order to ensure that the Hoof of the Soaring Dragon would not be seen. They would petrify or even murder anyone who saw the scar on their backs, aside from themselves or the three people who rescued them and know about their hideous past.
Rulers of the Women Tribe
As Hancock became the new empress of the tribe, with her sisters as her seconds-in-command, she became captain of the Kuja Pirates. After a single campaign Hancock was invited to be a member of the Shichibukai. She agreed to it and formed a treaty to protect the rest of her clan from any more intruding outsiders from entering their homeland, Amazon Lily.
However, despite going that far to protect her tribe, the trauma of her past had ruined Hancock's innocence, and she became uncaring and cruel to anyone but her sisters. In fact, she was willing to forfeit her position as Shichibukai and allow the treaty to be nullified, as she despised the World Government for being responsible for her terrible past.
The Gorgon Sisters held a deep-rooted hatred towards men being that the first man they ever saw was the one who branded them with the Hoof of the Flying Dragon. They believed all men to be selfish and cruel and would hold that belief for years.
Amazon Lily Arc
Years later, when Monkey D. Luffy was sent to Amazon Lily by Bartholomew Kuma after the Straw Hat captain attacked a World Noble, Luffy accidentally saw the mark on Hancock's back, prompting the Gorgon Sisters to kill him. However, after Luffy selflessly protected their backs from being shown to the rest of the tribe, as well as willing to forfeit his own chance to leave the island to save some petrified Kuja members, the Gorgon Sisters' idea of men changed.
When hearing that Luffy has struck a World Noble, Hancock, for the first time in years, allowed her soft and compassionate side to resurface. Luffy's actions even affected her to the point that she fell in love with him. She was willing to help him save his brother, Portgas D. Ace, who was nearing a public execution, even if it meant for her to return to the World Government that haunted her memories for years.
- One Piece Manga and Anime — Vol. 53 Chapter 517 (p. 14-15) and Episode 411, A Kuja telling a younger member about the falsified legend of the sisters.
- One Piece Manga and Anime — Vol. 53 Chapter 521 (p. 12-15,17-19) and Episode 415, The true past of the three sisters revealed.
- One Piece Manga and Anime — Vol. 53 Chapter 522 (p. 6) and Episode 416.
- One Piece Manga and Anime — Vol. 53 Chapter 516 (p. 8-19) and Episode 410, Hancock being threatened by Momonga for noncompliance.
- One Piece Manga and Anime — Vol. 53 Chapter 522 (p. 14-19) and Episodes 416–417, The sisters are changing due to Luffy.