A schoolgirl named Carol, and a close friend of Filia. However, one day, she was snatched up by Lab 0's operative, Valentine, as part of Project:Painwheel. Her very soul was weakened to prevent fighting back, and she was equipped with two Parasites - the Gae Bolga, which protrudes tough barbs out of her body, and the synthetic Buer Drive, a lightweight four-bladed device. She was also injected with Skullgirl blood to further strengthen her. To keep the reins in, Lab 0 director Brain Drain used his psychic powers to take command.
Wracked in pain and anger in her new form, Painwheel shows the face of a hateful monster. However, her hatred is mainly centered on Valentine, the one who turned her into this to begin with. Even when in combat, she tries desperately to keep control of herself. Peaceful, happy memories seem to relax her.