Raised to be an assassin ninja by the Hand, Kwannon was baptized as such to be "the enemy of peace". After falling in love with a boy and giving birth to a daughter, she displeased her masters, who in turn killed her lover and took her daughter away from her, as a lesson of mercy. As a mutant telepath, she built herself a notorious reputation as a killer who could "hear thoughts", being a loyal member of her clan. However, after so much psychological torture, Kwannon turned against her masters and assassinated them, finally breaking free.
Kwannon eventually became the prime assassin of Japanese crime lord Nyoirin as well as the lover of Matsu'o Tsurayaba, a high-ranking member of the Hand. When the interests of Nyoirin and the Hand came into conflict, Kwannon was honor-bound to face her lover in combat. During the battle, she fell from an ocean cliff and suffered injuries that left her brain-damaged. No hope for recovery was left for a comatose Kwannon, much to Tsurayaba's dismay.
Shortly thereafter, the telepathic X-Man Betsy Braddock, a.k.a. 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. To save Kwannon, Tsurayaba sought the help of the sorceress Spiral, a begrudging servant of Mojo (who had shown a marked interest in Psylocke prior to these events). Tsurayaba believed that Kwannon's limited psychic powers would allow her mind to withstand contact with a high-level telepath like Psylocke. Spiral, penchant for trickery and deception, transferred the two women's minds into each other's bodies, instead of simply recovering Kwannon. Believing Psylocke was Kwannon, Tsurayaba attempted to manipulate her into becoming the Mandarin's second-in-command. However, an encounter with Wolverine enabled her to break free of his mind control and rejoin the X-Men.
Meanwhile, Kwannon was recovered by her employer Nyoirin with the assistance of Spiral. The merge of bodies and minds between the two women led Kwannon to believe that she was truly Betsy Braddock. After months under Nyoirin's care, she was sent to the United States to confront Psylocke. As she infiltrated the X-Mansion and attacked Psylocke, the X-Men intervened. Kwannon (now assuming the codename "Revanche") claimed that Psylocke was not the real Betsy Braddock, but 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. The X-Men then left for Japan to uncover the truth. Reading Nyoirin's diary, they learned 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. Confronted by the X-Men, Nyoirin told them to search for Tsurayaba, but, as he was found, he revealed nothing about what had truly transpired.
Revanche returned to New York with the X-Men, becoming member of the team, much to Psylocke's discomfort. During a mission to an island which housed a colony of Legacy Virus victims, Revanche revealed she had also contracted the deadly disease. As the disease progressed, her telepathic powers were slowly enhanced, allowing her to cut through the confusion and distortion of her own memories. Certain of her real identity, Kwannon chose to leave the X-Men, but not before forcibly removing the bionic eyes Mojo had implanted in Braddock's body years before, severing her connection with Spiral. Finding her back in Japan and close to death, Kwannon asked Tsurayaba to end her life swiftly, so she would die of her own will and not as a victim of the disease. Matsu'o Tsurayaba killed Revanche with a tantō. As she died, she left a portion of her psionic energies within Tsurayaba, which allowed him restore Psylocke's mind and memories, making her full again. Kwannon's epitaph read "Kwannon, love that transcended body and soul".
When Braddock was attacked by the psychic vampire Sapphire Styx, who absorbed her soul into herself, her unconscious body was left apparently lifeless. After Psylocke managed to recreate her original body, her previous body was later reanimated, inhabited by Kwannon once again.
Kwannon's path would cross the X-Men again when the X-Men took on the latest incarnation of the Brotherhood of Evil Mutants that reappeared in East Transia. As the X-Men found out that their leader, Magneto, was actually the clone Joseph, Kwannon decapitated him with her katana. She then claimed to the X-Men she was trying to remember them and that she was "nothing", as translated by Wolverine from Japanese. She alleged that she had killed Joseph because he was manipulated into being a weapon to be used to erase mutants from the world.
Though the X-Men incarcerated Kwannon in their hideout, she was freed by Wolverine, who wanted her help in avenging Wolfsbane's death. Kwannon tracked Wolfsbane's killers and shared their memories with Wolverine, who in turn killed them after a brief confrontation against O.N.E. agents. She also assisted Wolverine in a fight against Emma Frost's new Hellfire Club, being defeated by Mystique after she tormented her with Braddock's visage.
Claiming the codename "Psylocke" for herself, Kwannon became a citizen of the mutant nation of Krakoa, which she considered a peaceful paradise that had no place for her. There, she experienced the apparent murder of her long lost daughter by a threatening artificial intelligence called Apoth. Since Krakoa was on a severe lockdown after the murder of Professor X, Psylocke turned to Mister Sinister for help in reaching Apoth. She recruited X-23 and Cable for her mission and the group learned in Japan that Apoth was using children to disseminate a technological drug called Overclock. Sanctioned by Sinister, Psylocke promised to bring Apoth to him if her mission was kept hidden from the Quiet Council of Krakoa. The group then found Apoth in Brazil, where Psylocke communed with Apoth and learned that, back when she worked as an assassin, she was responsible for its conception. Sinister modified Overclock to allow Psylocke to interact with Apoth on a cyberspace. Psylocke killed Apoth and, as promised, delivered its remains to Mister Sinister.
Following the Apoth incident, Psylocke was assigned to monitor Mister Sinister's new team of Hellions, composed of mutants who were too violent or troubled to be around the rest of the Krakoans. Their first mission led them to taking down Mister Sinister's orphanage, which was a cover for Sinister's still active Marauders cloning farm. When Kwannon and the Hellions arrived, they were met by the Goblin Queen, who had been magically and psychically torturing and controlling the Marauders. After a swift defeat, most of the Hellions were captured, except for Psylocke and Wild Child. Believing Psylocke was faulting as the alpha of their "pack", Wild Child attacked Psylocke, but met a quick defeat and was forced to accept her as the one in charge. Psylocke then managed to free her fellow Hellions, and the Goblin Queen was shot dead by Greycrow, allowing the rest of the Hellions to escape safely to Krakoa.
Before the start of a sword tournament, that was set up to settle matters between Krakoa and Arakko, the Hellions were tasked with infiltrating and sabotaging Arakko's forces. In Arakko, they learned not only that the contest had already started as they brutally fought the Locus Vile but also that their mission was a ruse to collect Arakki genetic material for Sinister. Psylocke was manipulated by Sinister into abandoning some of the Hellions in Arakko and return to Krakoa with DNA samples of the Locus Vile. Arriving in Krakoa, she was murdered by Mister Sinister as a way to cover his deceiving actions. After being resurrected, most of the Hellions questioned Sinister's take on Arakko, but he was fiercely defended by Psylocke. It was then revealed that her loyalty came from the fact that Mister Sinister had recovered Psylocke's daughter, now living a cybernetic existence, from the Apoth's remains she had delivered to him.
Later on, Psylocke's loyalty was tested again when Mister Sinister arranged for the Hellions to be kidnapped by Arcade and tortured by Mastermind as part of a trick to take over the Murderworld. In a nightmarish mental trap, Mastermind forced Kwannon to believe she had spent decades of her life being constantly hunted by Braddock. After Arcade was defeated and the Hellions were set free with no memories about what had really transpired, Mister Sinister told Psylocke he was working to restore her daughter in Arcade's Murderworld. He also claimed the Quiet Council would have his research destroyed if they ever learned about his activities. With no choice, Psylocke watched as Sinister and Mastermind sent the Hellions home believing they had escaped on their own in order to protect her daughter.
Having worked through her anger in this mental simulation, Psylocke teamed up with Excalibur after Braddock went missing as a result of her fight against Isca the Unbeaten. Though Elspeth Braddock retrieved Braddock's spirit, Rictor failed to return her to her body. Psylocke set Braddock's spirit free and chased her down in Avalon. As the two women met, they finally had the opportunity to discuss their sorrowful connection. Psylocke offered to temporarily host Braddock's psyche once again in order to fully resurrect her. Excalibur then learned that Braddock's body had been previously possessed by Malice. Psylocke, with newfound sympathy for Malice's situation, tracked her down on Krakoa and telepathically fought her and executed her by destroying her necklace. Malice was then revived in a new body and had a second chance at life.
Psylocke's growing, unspoken resentment for Mister Sinister reached a breaking point when the team were attacked again by the Locus Vile, who had come to Krakoa to retrieve the samples Sinister had stolen from them. Tarn the Uncaring revealed to the whole team that Sinister had misled them. The Hellions tried to attack Mister Sinister, but were distracted by an army of his clones. Sinister left with the clone he had sent to Amenth through an illegal gate to Murderworld that only he could access, leaving Psylocke behind in anger and defeat. Psylocke shared the truth about Sinister's schemes to the Hellions. After evading the Locus Vile, the group went to confront their traitorous master. Though Havok and Greycrow wished to destroy the facility, Psylocke begged them not to, finally revealing about her daughter. However, Empath intervened and, under Emma Frost's orders, caused Havok to bring Psylocke's only chance of getting her daughter back to the ground. Pulled out of the wreckage by the X-Men, the Hellions returned to Krakoa for healing. As the Quiet Council decided to cover up Mister Sinister's wrongdoings for his relevance to the mutant society, Psylocke decided to give up on Krakoa and the Hellions, aiming to continue life as an assassin looking for death.
Captain of Krakoa
Nevertheless, Psylocke was still elected by the Quiet Council to join the Great Captains of Krakoa even though she planned to leave the island. However, before abandoning Krakoa, she was informed Nanny had adopted an android baby which had been recaptured by the Right, and Orphan-Maker had gone to Arizona on a one-man mission to retrieve it. As a Captain of Krakoa, she insisted to help Orphan-Maker by herself, but the rest of the Hellions decided to back her up. They went to the Right's Zeta base, and after a brutal battle Nanny was killed by the robotic child, while Orphan-Maker lost control and killed two nearby human rangers. Orphan-Maker was placed alongside a resurrected Nanny in the Pit of Exile following the Quiet Council's decision, contrary to Psylocke's attempts to prevent this. Afterwards, the Hellions were disbanded. Kwannon decided to remain on Krakoa as a Captain, contemplating her potential to be a better person alongside Greycrow. Not long after, Psylocke was invited by Captain Kate Pryde to join the crew of her Marauders, which she accepted.
Telepathy: As a mutant, Psylocke displays telepathic abilities which enable her to read minds, communicate with others by broadcasting her thoughts psychically and other talents. Originally, she had low-level empathic/telepathic abilities. After having her body switched with Betsy Braddock, contracting the Legacy Virus and being a member of the X-Men, her powers developed significantly.
- Psychic Katana/Knife: In Betsy Braddock's body, she physically manifested her telepathic powers as a blade, created as an ornate psionic katana. The blade could disrupt the autonomic nervous systems of other living beings, incapacitating them instantly. Kwannon 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. After returning to her original body, she altered such a manifestation to one similar to Betsy's psychic knife, the focused totality of her powers.
- Telepathic Detection: With her psionic senses, Psylocke can track other sentient beings by their psionic emanations. She did this to locate Wolfsbane's killers.
Telekinesis: On various occasions, Psylocke has demonstrated mid-level telekinesis, enabling her to levitate, move and manipulate objects and matter with her mind.
- Flight: Psylocke can use her psychic powers to levitate and even fly at higher speeds. She floats in the air when meditating and once created a pair of psionic butterfly wings to fly a longer distance.
Master Martial Artist: Psylocke is highly skilled in different ninja fighting techniques and other martial arts, including sword fighting, as she was trained from very tender age and worked as an assassin for years.
Untrained Telepath: Being relatively untrained in the use of her telepathy, Psylocke rarely employs her abilities beyond generating psionic blades and unconsciously clouding the minds of others.
As an expert swordswoman, Psylocke owns at least a pair of Japanese traditional katanas.
X-Men Blackbird, Krakoan Gateways.
- The name "Kwannon" (観音, in Kanji character) is an archaic transliteration of her namesake, the bodhisattva of mercy, which would be rendered as "Kan'non" in current Japanese, pronounced as [kanːoɴ].
- The name "Revanche" ([ɹəˈvɑ̃ʃ]) is not simply an alternate derivative of the word "revenge," but rather means a "policy designed to recover lost territory or status." From French origin, it is pronounced as [ʁəˈvɑ̃ʃ] in French.
- The name "Psylocke" ([ˈsaɪ.lɑːk] SEYE-lok) is assumed by some fans to be a wordplay with the words "psyche", "key" and "lock". As "psyche" is pronounced as "psy-key", "Psylocke" would be pronounced as "psy-lock".