Her origins unknown, the woman known as Kwannon was first seen as the prime assassin of the Japanese crimelord Lord Nyoirin, as well as the lover of Matsu'o Tsurayaba, a high-ranking member of a group of ninja mystics called the Hand.
When the interests of Nyoirin and the Hand came into conflict, Kwannon was honor-bound to face her lover Matsu'o in combat. During the conflict, she fell from an ocean cliff and suffered injuries that left her brain-damaged and comatose with no hope for recovery. Shortly thereafter, the telepathic X-Man Psylocke was found washed up on the shore of the Hand's island base in the South China Sea after passing through the Siege Perilous. Matsu'o sought the help of the sorceress Spiral, a begrudging servant of Mojo, to save Kwannon (for reasons unknown, Spiral and Mojo have shown a marked interest in Betsy Braddock prior to these events; Mojo gave her the codename Psylocke when he attempted to make her his servant, and Spiral was responsible for implanting her with bionic eyes to replace the ones she lost, which acted as interdimensional cameras for a time, recording her adventures with the X-Men). Spiral informed Matsu'o that it would be possible to use Psylocke's telepathy to restore Kwannon's mind. Kwannon's limited empathic power allowed her mind to withstand contact with a high-level telepath like Psylocke. Matsu'o agreed, unmindful of Spiral's penchant for trickery and deception. Spiral used her magicks, combined with the alien technology of her Body Shoppe to transfer the two women's minds into each other's bodies, also intermingling their DNA. The result of this merge was that they now physically resembled each other and each possessed half of Psylocke's mutant telepathic abilities. Matsu'o tried to manipulate Psylocke, whom he thought was his lover Kwannon, into becoming the Mandarin's second-in-command, but an encounter with her teammate Wolverine enabled her to break free of his control and eventually rejoin the X-Men.
Meanwhile, Kwannon was recovered by her employer Nyoirin (with the assistance of Spiral). Her new body was retrained in the martial arts, and she was sent to the United States to confront Psylocke. The merge of bodies and minds between the two women had left each with memories and personality traits of the other, leading Kwannon to believe that she was truly Betsy Braddock. She infiltrated the X-Mansion and fought Psylocke with a psychic katana that functioned in the same manner as Psylocke's psychic knife, cutting through the mind and disrupting the nervous system of it's target. When the X-Men arrived to aid Psylocke, Kwannon (now assuming the codename "Revanche") claimed that Psylocke was an impostor. The other X-Men were unable to determine the true identities of the two women; according to Wolverine, their scents were identical, and Psylocke, subject to manipulation many times in the past, was unwilling to allow Professor X to telepathically probe her mind in search of the truth. Finally, the two women left for Japan to uncover the truth, accompanied by Gambit and Beast. Revanche surprised her fellow companions with her ability to read and speak Japanese perfectly, a skill the real Betsy Braddock never acquired. After a brief confrontation, it was revealed that Kwannon was supposedly the first person to happen upon the unconscious Betsy Braddock after her re-emergence from the Siege Perilous portal. Amnesiac and disoriented, Psylocke's telepathy ran unchecked and fused the two women's minds together. This story was later proven to be the result of false memories generated by Kwannon after being lied to by Matsu'o and Lord Nyoirin. The group found and confronted Matsu'o, but he would reveal nothing about what had truly transpired.
Revanche returned to New York with the X-Men, becoming an unofficial member of the team for a short time. On a mission to an island which housed a colony of Legacy Virus victims, it was revealed that Revanche herself had the deadly disease. The Legacy Virus slowly increased her telepathic ability, allowing her to cut through the confusion and distortion of her own memories, revealing the truth: that she was in fact Kwannon inhabiting Betsy Braddock's original body, as Braddock now inhabited hers. It was also discovered that Kwannon was unconsciously creating psychic confusion in the minds of her teammates concerning her and Psylocke's true identities. Close to death, Kwannon asked Matsu'o to end her life swiftly, in atonement for his transgressions against her and Psylocke, and so that she might die of her own will and not as a victim of disease. Matsu'o killed Revanche with a tantō. With Kwannon's death, Psylocke's full telepathic potential was returned to her. Revanche also left a portion of her psionic energies within Matsu'o, who used it at her behest, removing Kwannon's fractured memories and personality traits from Betsy Braddock's mind, and restoring those of Betsy's that were possessed by Kwannon.
Kwannon's epitaph, left by Psylocke and Matsu'o on her grave in Matsu'o's garden, read "Kwannon, love that transcended body and soul".
Revanche recently resurfaced again when the Sisterhood of Mutants stole her corpse and used a magical psychic spell to transfer the life-force of Psylocke into her corpse and reanimate her body. Her reanimated body was under the control of Madelyne Pryor and she was forced to fight the X-Men on her behalf. She was later killed by Psylocke in a battle of psychic wills and Psylocke's mind was returned to her intact Asian body.
Telepathy Upon inhabiting Psylocke's former body, Revanche gained telepathic abilities which enabled her to read minds, communicate with others by broadcasting her thoughts psychically.
Psionic Katana She could physically manifest her telepathic powers as a blade (like Psylocke's psychic blade), but instead of a small energy dagger she created an ornate psionic katana. The blade could disrupt the autonomic nervous systems of other living beings, incapacitating them instantly. Revanche could also use her psychic katana to force her way into an opponent's mind and reveal any thoughts that were originally shielded from her telepathic powers, including those of other telepaths.
Mind Control Revanche can control the minds of others by using her telepathic abilities gained after inhabiting Psylocke's body.
Illusion Casting With the use of her telepathic abilities gained after inhabiting Psylocke's body, Revanche can cast realistic illusions altering the perceptions of its targets.
Empathy Originally, Kwannon possessed a low-level empathic talent that allowed her to sense the emotional state of others.