Operation Zero Tolerance
Cecilia Reyes decided to become a doctor when her father was gunned down in front of her as a child, and she was unable to do anything to help him. The X-Men tried recruiting her when it was discovered that she was a mutant, but Reyes had no interest in being a superhero. When she was targeted by Operation: Zero Tolerance, a government-backed anti-mutant task force, she was forced to join forces with the X-Man Iceman and other mutants to escape New York City and track down Bastion, leader of Operation Zero Tolerance.
Becoming an X-Man
She refused to join the X-Men at first, making an attempt to return to her normal life. After meeting with problems with racism and both encouragement from Daredevil and an encounter with the villainPyro, Reyes reluctantly joined the X-Men. She had several adventures with the team, combating the Ru'tai and the Shadow King. She usually did not bother with a costume, wearing either the yellow and blue training uniform or, on one occasion as a joke by Beast, an old costume of Wasp's. It was while wearing Wasp's old uniform that Reyes became involved in a battle with the X-Men's frequent enemy, the N'Garai. Reyes mostly ran away, but was saved (and mocked) by the X-Man rookie Marrow. She was eventually sucked into the N'Garai dimension, to be experimented upon, but her force field saved her from the cutting instruments. She escaped with the rest of the X-Men and the civilians they had saved.
Reyes was tempted by the Shadow King by offers of a new life, but managed to resist the villain's offer. Reyes did not find costumed adventuring suitable for her, and left to set up her own medical practice.
Later, she was caught up in the X-Men's battle with the Neo, a villainous group of mutants who claimed to have evolved beyond the level of other mutants. Reyes was trapped in the Neo's fortress below New York City and used a street drug called Rave to make her mutant powers more destructive, ensuring her survival. The X-Men rescued her, and the telepathic Professor X helped her kick her addiction to Rave during a detox period back at the X-Mansion.
Reyes last appearance with the X-Men was at the time when Beast discovered the cure to the Legacy Virus. She was the one to discover Colossus dead after injecting himself with the cure. Reyes attempted to revive him, but was unsuccessful.
Later, she was seen as a prisoner at a mutant concentration camp run by the Weapon X program, called Neverland. There she attempted to use her medical expertise to help out the other prisoners. She was apparently killed off panel when a brainwashed Agent Zero destroyed the camp,Cite error: Invalid
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In it has been revealed that Cecilia's older non-mutant brother, Colonel Miguel Reyes, had been assigned to head O*N*E security on the Xavier School grounds, with the purpose of finding out the fate of his sister.
After M-Day and her escape from Neverland, Cecilia volunteers at local homeless shelters as well as working out of her apartment. According to Bobby Soul, she works off the record and under the table. The NYX teenagers bring an injured Tatiana to her for help. During their visit to her apartment she doesn't reveal to the teens that she used to be an X-Man. After treating Tatiana, she offers them a place to rest while she goes out for a few hours. Unaware Kiden Nixon is following her, she calls up Beast to ask a favor. Later when Cecilia returns with groceries, she finds the teens have left.
Sometime after these events, Cecilia moves to the X-Men's new base of operations; Utopia. When Magneto decides to bring back Shadowcat as a good will gesture, Cyclops asks specifically for her to help treat him of any injuries he might have suffered.
The Five Lights
After the events of Second Coming, Cecilia is partnered with Psylocke and sent to Mexico to locate the second of the Five Lights; the first mutants to manifest powers since M-Day. After sedating Gabriel, she informs his parents of what is transpiring and offers him help from the X-Men. Psylocke comes to the room and explains that something has happened, Gabriel's manifesting speed powers caused him to move so fast he is invisible to the naked eye. Psylocke taps into Cecilia's powers to create a force field around his room so they would not lose him before Hope Summers could arrive to help.
Powers and abilities
Psioplasmic Bio-Field: generates a psioplasmic bio-field, increasing her durability. The field extends six inches from any point on her body. This field constantly surrounds her body at every given moment, completely invisible, and only takes on a glass-like translucency when subconsciously activated by a threat. The field reacts to kinetic impact, energy signatures, certain psionic forces, temperature changes, etc. The bio-field is an extension of Cecilia's body, and so she feels the attack as its effect is dispersed over the field. Her power is subconscious, meaning it protects her from harm whether she wants it to or not, or is aware of the harm or not. However the field does not activate for threats it does not "know," since her power is mostly instinctive. For instance, Cecilia might know touching Rogue is bad, but her field would not automatically protect the doctor from contact with her. It's unknown if the field has any kind of "learning capacity" that registers when a new sort of threat bypasses it's protection. Eventually Cecilia will also learn how to manifest the field at will, as a weapon. Surrounding her fists with psioplasmic force can increase the bludgeoning power behind her punches; she will be able to extend razor pointed spikes from the field, expel the field outward in a hammer-like ram, etc. More recently, she has learned to control the shape of her fields
Cecilia was apparently killed off panel when a brainwashed Agent Zero destroyed the camp, and her death was later confirmed in the letter column of New Excalibur #1. Mike Marts contradicted this in an interview on uncannyxmen.net, stating that if Cecilia would be dead they would show it on panel, and therefore Cecilia was not yet considered deceased at that time.