Hollow, also known as Penance, is mutant and former member of the Generation X X-Men team. Her backstory is convoluted and has been retconned several times. Broadly, she is a mutant with red diamond-hard skin and extended super-long razor-sharp claws on their fingers, toes, and hair follicles. She also has a unique capacity to serve as a host and storage for the minds and bodies of others. Additionally, Hollow is also mute. Initially, Penance was a feral and skittish escapee from a vampiric mutant called Emplate, who fed on and abused his prisoner, using her as a prison for his sister, M (Monet St. Croix). A convoluted series of events lead to the purging of M and her family from Penance, who had begun to become socialized thanks to her teammates. After Generation X disbanded, she later appeared with the Losers, a California-based team of miscellaneous young superheroes, who rescued her from a lab where she was being held for unknown purposes. The Losers were eventually brought into the Avengers' new superhero training program, Avengers Academy. She last appeared in the pan-mutant community of Utopia of the San Francisco coast.