Stacy Turner thought any place had to be better than home. When her parents weren't fighting, her father was devising restrictive punishments in an effort to "get her on the right track." She also saw no reason to stay in school. So one night after fighting with her father she ran away from home. However, living on the streets of Chicago turned out to be a lot harder than she thought it would be. One night while walking down a dark alley, she found herself surrounded by a gang looking for something to steal. Turner only had a few dollars on her which she knew wouldn't be enough for them. Terrified, she snapped, and her powers manifested in the form of telekinetic knives that ripped her attackers apart. Stealing their wallets and using the cash in them, she bought a ticket for the first bus out of town.
Stacy stayed on the run, moving from city to city as the mood struck her. When she landed in Millennium City for a few days a man named Trace approached her. Trace not only knew who she was, but he also knew what she could do and what had happened in Chicago. He told her he could take her someplace safe, where doctors would help her learn how to use her powers safely and no one would ever be able to hurt her again.
Stacy was suspicious, but Trace eventually won her over. He took her to meet Dr. Sebastian Poe, who taught her new ways to use her powers, and Poe's student Psimon, with whom she felt an instant connection.
Stacy, now calling herself Mind Slayer, became one of PSI's most feared assassins. And when Psimon approached her about joining him in taking over the organization from Poe, she instantly agreed. Now she works in the field on behalf of PSI, but will return to Psimon's side to act as his personal bodyguard.
Mind Slayer is loyal to the death to Psimon. She does not care about anyone else. She rarely speaks to anyone but Psimon, and reacts harshly and sometimes even violently to any attempt to engage her in conversation. Other members of PSI have learned to keep their distance from her as much as possible.
Mind Slayer's powers are all variations on telekinesis, from straightforward mental grabs to shields and psychokinetic fingers. Her favorite uses of her powers are the razor-sharp blades she fashions from pure mental force and uses to slice her opponents to pieces. She will not hesitate to use lethal force to complete a mission for PSI, and sometimes she'll kill just for the fun of it.