For every kill she has a tattoo, and she is covered in ink. Subject Zero has been around; ran with gangs, joined a cult, and kept the haircut. A powerful biotic with a mysterious past, not much is known about Subject Zero other than she is drawn to brutality and violence.
Her emotional instability doesn't help the fact that she can lift and discard enemies like trash with her biotic powers. She's dangerous, unstable, and extremely violent, exactly what Commander Shepard needs for his suicide mission. Subject Zero's skills and abilities will be a valuable asset to Shepard's team, that's if he can keep her under control.
