Sarah Stacy

Prior to his death, Harry Osborn devised a cruel plan to torture both his father Norman and his former best friend Peter Parker. With the help of Mendel Stromm, he built a secret laboratory in the Parisian Osborn Manor and genetically-engineered two bodies spliced from Norman and Gwen Stacy's DNA: a boy named Gabriel and a girl named Sarah. They were created to torture Peter, Norman, and Mary Jane Watson by making them believe Gwen had cheated on Peter with Norman and got impregnated by him as a result, with Harry going as far as to hiring Mysterio to hypnotize both Norman and Mary Jane to implant false memories which corroborated that narrative. The twins were raised by an artificial intelligence designed from Harry and Norman's minds, who inherited Harry's revenge plots after he died, to believe that lie as well.

Because of a genetic flaw caused by Norman's enhanced blood, the Stacy twins aged at a rapid rate, resulting in their premature deaths. Taking advantage of that, Mephisto, the Hell-Lord to who Norman had sold Harry's soul in exchange for achieving glory, acted through the Osborn A.I. to bring them back to life again and again, forging them in the literal flames of Hell while they were in his realm. He planned to eventually use them as his pawns to claim Spider-Man's soul, thus averting a future he saw in which the hero's daughter with Mary Jane ended his reign of terror once and for all.

In the meantime, Sarah and Gabriel, ignorant of the truth about themselves and having aged into adulthood within a few short years, were released into the outside world. There, they were manipulated by either the real Norman or the Osborn A.I. into thinking Peter was their real father and also the man responsible for their mother's death. Sarah's striking resemblance to Gwen caused confusion to Peter when he unmasked her after she tried to kill him. From the combination of clues on a letter they used to draw him out and the implanted memories Mary Jane had of Gwen and Norman's arguing while Harry was hospitalized, Peter attempted to convince the twins of Norman's lies. While Gabriel refused, Sarah remembered that Peter had dug up Gwen's grave to get a DNA sample, and realized that Norman never even bothered to run his own DNA against theirs, and concluded Norman "knew" that they couldn't be Peter's children. Unfortunately, the police intervened and opened fire on all of them before Spider-Man could deescalate things, and Sarah was shot while her brother fell into the river.

Taken to the hospital, Sarah's body refused all blood transfusions until Spider-Man offered his in speculation that his own unusual blood samples would help to stabilize the Goblin serum in her bloodstream. After Sarah regained consciousness, her brother crashed through the hospital window having taken a new Goblin serum to become the Grey Goblin, and dragged Peter out to kill him. In his weakened state, Sarah was able to save Spider-Man by shooting her newly insane brother's Goblin Glider, causing him to crash and lose his memory.

Later, Sarah secretly took Gabriel back to Paris, and cared for him at the Osborn estate until the pressure from local drug dealers to repay a debt by her brother became too much and she attempted suicide. Peter was called to Paris by the hospital as her emergency contact. While he was with her, MJ went looking for him at the estate, and inadvertently caused Gabriel to escape in a crazed state. After cutting a deal with Interpol to catch the dealers, Sarah joined the organization to attempt to find her brother.

After some time, Sarah and Gabriel died from their genetic instability, with an unknown set number of clones being created subsequently. When the time to hatch his plan came, Mephisto gave the Stacy twins demonic powers and seemingly bonded them to the real Harry's soul and/or the Osborn A.I., granting them access to all of Harry's memories and hatred. Sharing the Kindred identity, Gabriel and Sarah tortured Spider-Man for months under the guise of Harry Osborn, motivated by memories of the hate Harry once held in life.

Once more living on Earth, Gabriel and Sarah shared the mantle of "Kindred" and haunted Peter Parker as the damned soul of Harry Osborn, and also manipulating Norman's awareness of facts into believing such. During Mysterio's psych review in Ravencroft, Sarah appeared apologetic and allowed him to mutter her real name. However, she apologized again and killed him,] before learning it was an escape by Mysterio from Ravencroft. Although angry that he shared Kindred's name, she instead spared him in a plan to give Mary Jane a job in film. During the symbiote invasion, Sarah visited Norman's cell in Ravencroft to vent, but also implant a parasite that stunned Norman as Carnage later, to help Peter win in a fight. She ventured into Hell to make Stanley Carter a minion of Kindred's on earth, sent on a violent campaign, culminating in cleansing Norman before Gabriel harvested the combined sins to possess the Order of the Web.

With Gabriel's capture, Sarah continued the mission and abducted Carlie Cooper before she revealed the real Harry Osborn's corpse to Mary Jane and imprisoned alongside Harry's clone before moving to guide Otto Octavius from afar in reassembling the original Sinister Six. As the Sinister War began, Sarah had Mysterio abduct Mary Jane and reveal to her how she was brainwashed with false memories as part of a posthumous plot of Harry's. Sarah then revealed her true face before explaining the cloning experiment that created her, the connection to their "previous" encounter, and how Peter was to be punished. After Peter was portaled to Paris, their battle culminated in a final confrontation where, despite their best efforts, the Kindred were ultimately unable to break Peter's spirit as Mephisto wanted and dismissed them. With the demon keeping them genetically stable, their rapid-aging disease was once more active for their failure, and Sarah died with her brother beside Peter.