Medium the Fingernail is a Bandersnatch assassin operating in Mardock City. He collects fingers from his victims, adorning himself with them as a necklace. He replaces his own fingers with those taken from targets, carrying spare fingers in a case or glass container for immediate replacement. His practice also includes removing victims' feet, suggesting his collection may extend to toes.

During Bandersnatch operations, he spearheads assaults, eager to eliminate targets swiftly to acquire desired body parts. His aggressive actions fuel violent confrontations, including an attack on protagonists Rune Balot and Dr. Easter at their headquarters, during which he sustains injuries.

Across the anime film trilogy, novels, and manga adaptations, Medium the Fingernail exhibits no documented background story, personal history, or character development. His role remains consistently that of a secondary antagonist within the Bandersnatch group, defined solely by his pattern of violence and anatomical collection, with no elaboration on motivations, origins, or evolution.