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 its 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 Xavier 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".
Upon inhabiting Psylocke's former body, Revanche gained telepathic abilities which enabled her to read minds, communicate with others by broadcasting her thoughts, control the minds of others, and create realistic illusions by altering people's perceptions. 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.
Being relatively untrained in the use of her telepathy, Revanche rarely employed her abilities beyond generating psionic blades and unconsciously clouding the minds of others.
In the 6-part 2005 limited series, X-Men: Age of Apocalypse written by Akira Yoshida and drawn by Chris Bachalo, which was part of Marvel's celebration of the 10th anniversary of the original AOA, a counterpart of Psylocke was introduced, who was most likely also the AOA version of Kwannon. This Psylocke is a ninja who looks and acts almost exactly like the original pre-transformation version of Kwannon in 616, except with black instead of purple hair, and with the ability to generate psychic blades (an ability manifested by 616 Betsy Braddock only after she body-switched with 616 Kwannon), which she used to make the AOA's version of X-23, Wolverine's daughter Kirika regain her suppressed memory. After helping the X-Men in thwarting the machinations of Mister Sinister, she joined the other Japanese members of the X-Men (Sunfire, Kirika, and Silver Samurai) in migrating to the Clan Yashida's refugee colony of New Japan.
Revanche has a cameo in the X-Men based fighting game X-Men: Next Dimension. In the game, there are actually two separate Psylocke characters, one appearing as the telepathic Psylocke (called "Betsy" in the game), and a second, appearing as the telekinetic version of Psylocke (sporting her trademark psionic katana). Though neither character is technically Kwannon, one of the telekinetic Psylocke's costumes is the Revanche costume. The Revanche costume also alters the look of the psi-katana, making it white with a pale pink aura (while TK Psylocke, shown next to Revanche in the screenshot, has a rose colored energy blade)