Lady appears as a fair-skinned woman with short black hair and heterochromia, her left eye being red and her right eye, green. She typically wears a Darkcom trooper outfit.

Mary is the daughter of John Arkham and Kalina Ann. As a child, Mary loved action movies and imagined herself as a hero that fights against evil. One day, after seeing a movie with her parents, the family is attacked by a demon, but are luckily saved by a passing train. Following this incident and the failed attempt to report to the police, John became completely obsessed with studying demons, isolating himself from his wife and daughter in the process. Occasionally, Mary would look through the peephole into his study, but was too scared to open the door to confront him. Eventually, later that night, Mary saw that the door was wide open and approached it to see her parents arguing. Kalina tried to comfort Mary, but John injected himself with demon blood, transforming himself into a demon. He would then kill off Kalina and begin eating her dead corpse right in front of Mary. but Mary herself would attempt to fight back while holding a scalpel, but was quickly overpowered; however, the scuffle accidentally started a fire that quickly enveloped the entire room. As Mary would flee the building, as for her, her father would reach out for her but caught on fire and would seemingly die in the flames.

As a young adult, Mary approached and joined DARKCOM, she would quickly work her way up to become a lieutenant. Her group eventually began investigating a group of demons and tracked them down to a warehouse, where they killed the demons present. Before they left, a portal opened up and a man, followed by multiple humanoid demons exited. Darkcom trained their guns on the group as the man attempted to explain the situation; however, before he could finish, a much larger demon would burst out of the portal and began attacking the smaller demons, causing them to flee. This, in turn, led the Darkcom agents to kill all the demons present there and collapse the building, with the man seemingly dying in the carnage as well.