Very little information has been revealed about Mystek's life, prior to her first confrontation with the Ray. Seong was a young Korean woman, born in Queens, New York, who preferred to be called 'Barclay'. Her father was involved with some sort of sensitive work, and was captured (possibly by some form of government agency), leading her to fear federal agents and live in a general state of suspicion. At some point, she had an ally named 'Tank', who was later killed. During an undisclosed incident in Seoul, she developed intense claustrophobia. She had an enemy named 'War Locke', whom she killed in a place called 'Empire Valley'. Her costume was sculpted to resemble a male physique, in order to further hide her true identity.
Mystek was created by Christopher Priest. Hoping to spin her off into her own series, he featured her heavily in the Ray and Justice League Task Force during his runs as writer on those titles. When it became clear she would not be carried over into a solo title, he decided to kill her off it JLTF.
In Philadelphia, Seong owned Circuit Shack, an electronics store, and was residing in the basement. Raymond Terrill, secretly known as the Ray, went shopping at her store, setting off sensors which registered him as a powerful metahuman. Believing that he was sent to capture her, Mystek assaulted him, while he attempted to protect his identity by not directly confronting her. He ultimately used his solid light powers to create a simulacrum of himself, so she would believe that the Ray and Raymond Terrill were two separate individuals, and she did in fact relent.
Some time later, after seeing through his trickery, Mystek again pursued the Ray. She journeyed to his apartment, where she stumbled across his electron shield, a device which allowed access to the headquarters of the Justice League Task Force, of which Ray was a member. Seong was transported before the assembled JLTF, and, believing that they were a government agency abducting her for experimentation, she attacked. She blasted her way out of their headquarters and escaped.
Weeks later, J'onn J'onzz, the Martian Manhunter and leader of the JLTF, entered her store while in his human guise. Seong immediately determined his true identity, and flew outside to confront him. After a brief battle, J'onn explained to her that he had perceived her prior panic and recklessness as signs that she needed assistance, and, seeing some potential within her, offered her membership to his team. J'onn gave her an electron shield of her own and a new costume which also included sculpted male anatomy, convincing her that he knew the secret of her gender.
While she accepted J'onn's offer, her tenure was brief. Soon after joining them, the team left on a mission to the planet Xanthcar, where another member of the JLTF was being put on trial. The cramped space-fairing pod proved to be too much for the extremely claustrophobic Mystek, and, after over two days of travel, she panicked, blasting her way into open space. She soon suffocated and died.
Powers and Abilities
Mystek is a metahuman, who can process Quark Energy into blasts and other uses, including enabling flight. In their first encounter, L-Ron/Despero described it as "manipulating energy at a sub-atomic level, yielding a high-tolerance elastic proactive matter." Mystek later stated that she can use any electronic device as a 'window' to the proactive matter state her powers effect.