Harley Quinn (Arkhamverse)

An Arkham Asylum psychiatrist turned girlfriend to criminal mastermind the Joker, Dr. Harleen Frances Quinzel reinvented herself as the deadly criminal Harley Quinn after developing an affectionate obsession with the Clown Prince of Crime, becoming an accomplice to his nefarious schemes and a worthy opponent to the Dark Knight. Quinn rose in both power and viciousness after the death of her beloved Joker, taking command of the remnants of his followers and allying herself with the Gotham underworld's most notorious superpowers in a master plan to bring down the Batman.

Batman: Arkham Origins

 * See: Harleen Quinzel (Batman: Arkham Origins)

Batman: Assault on Arkham

 * See: Harley Quinn (Batman: Assault on Arkham)

Batman: Arkham Asylum

 * See: Harley Quinn (Batman: Arkham Asylum)

Batman: Arkham City

 * See: Harley Quinn (Batman: Arkham City)

Batman: Arkham Knight
After her plans for revenge were foiled by Batman and Robin, Quinn was incarcerated in Stone Ridge Penitentiary alongside the remainder of Arkham City's former residents, where she found herself still haunted by her boyfriend's demise. Determined to overcome her sorrow, Harley dedicated herself to moving on from the ghosts of her past, intending to start fresh as the Joker would want her to and ensuring his legacy is remembered in Gotham for eternity.

After Commissioner Gordon is infected with Joker Toxin as a part of the clown's post-mortem scheme, Batman brought Quinn into the ruins of Arkham City, hoping she could provide the antidote hidden in her old headquarters, the Sionis Steel Mill. Feigning guilt over her past crimes and a need to atone for them, Harley revealed its location, secretly leading the Caped Crusader into a trap as she had recruited Killer Croc into guarding the chemicals during her finals moments within the mega-prison. With Batman presumably dealt with, Quinn escaped into Gotham and located the Penguin, recovering from the fateful night in Arkham City, where she forged a partnership between their gangs, sealing the deal with a kiss.

Months later, after she and Cobblepot allied with Scarecrow in his plot to destroy Gotham and its vigilante, Harley traveled to Bludhaven to free Poison Ivy from imprisonment, fighting against the local police force.

Arkham Knight Profile
Dr. Harleen Frances Quinzel

An Arkham Asylum psychiatrist assigned to treat the Joker, Dr. Harleen Quinzel fell in love with her patient, assuming a deranged criminal identity of her own. She remained by Joker's side until his death in Arkham City, which she believes to have been at Batman's hands.

Grief-stricken and vengeful, Harley brutally reasserted control of Joker's gang as it threatened to fragment after his demise. Freed from Joker's domineering personality, she's become a dangerous, unpredictable new force in the Gotham City underworld.