Sublime

Sublime is an original fictional character.

Background
Clio Cardona was an in-patient at a long-term psychiatric care facility in Trieste, Italy, at the time she developed her mutant powers. Once she had been a vibrant, happy young girl, until she and her mother were among the 52 innocent people taken hostage in a bank robber gone awry. Young Clio was only five years of age at the time, and though she and her mother survived the 2-day ordeal physically unharmed, the graphic and violent deaths of several hostages, as well as all five bank-robbers-turned-hostage-takers killed in the final police rescue operation left her severely traumatized.

Suffering from severe dissociative post-traumatic stress disorder and a variety of compounding diagnoses, Clio was eventually moved to a facility that could provide her with around-the-clock care. There she remained until the day her mutation first presented itself, at which point she simply floated out the door to freedom. She may or may not have even been aware that she suffocated two orderlies to death along the way.

New Mutants: Last Class
Little is known about Clio's activities after leaving the facility. The X-Men sent a team to Trieste to petition Clio's doctors into releasing her into the care of the Xavier Institute, but by the time they arrived she was already gone. It was Wither who somehow managed to track the girl down and persuade her to join his cause.

Timeskip and the Last Stand
Clio eventually emerged as a member of Wither's Brotherhood of Mutants under the codename "Sublime". She remains an active member to this day, turning her lethal powers against the remnants of the Purifier army and their allies.

Powers and Abilities
Clio Cardona is a human mutant, though the relative potential of her mutation is unknown. She possesses the ability to fully convert her body and a small additional mass of organic material into a gaseous state consisting of varying concentrations of carbon dioxide and carbon monoxide. Colourless and odourless, she is almost impossible to detect with normal human senses in this form, and can move about freely through the air and can squeeze through all but perfectly airtight spaces. The only telltale sign of her presence is a slight drop in room temperature, as the conversion from solid to gaseous form consumes a significant quantity of energy from the surrounding environment; a rapid conversion also results in a sudden burst of air pressure as her total volume increases dramatically as her density decreases. She has such precise control over this ability that she has been known to reflexively and instantaneously convert herself to her gaseous form in response to injury or when sufficiently startled.

As Sublime, Clio is best known for suffocating her foes to death by physically entering their lungs while in gaseous form. By altering concentrations of carbon dioxide and monoxide, Clio can cause tremendous suffering to her victims, or kill them with no apparent discomfort at all.

Additionally, Clio is abnormally sensitive to changes in air pressure around her, effectively giving her enhanced hearing and awareness of her surroundings.

According to her medical records, Clio suffers from severe dissociative PTSD, histrionic personality disorder, and holophobia (the irrational fear of weapons, especially guns). She is fluent in Italian and speaks basic English.