Typhoid Mary, whose real name is Mary Walker, debuted as a villain in Marvel Comics' Daredevil #254 (May 1988), created by writer Ann Nocenti and artist John Romita Jr. She is portrayed as a mutant suffering from severe dissociative identity disorder, stemming from childhood trauma and abuse, which fragmented her psyche into multiple personalities. Initially introduced as an assassin hired by the Kingpin (Wilson Fisk) to target Daredevil, her origin involves a traumatic incident where, as a young woman, she was inadvertently harmed by Matt Murdock (Daredevil's alter ego), triggering the emergence of her violent alter egos and a deep-seated resentment toward men.

Typhoid Mary's character is defined by her contrasting personalities: the meek and pacifistic "Mary," the seductive and aggressive "Typhoid Mary," and the brutally sadistic "Bloody Mary," who exhibits extreme misandry. Her mutant abilities include low-level telekinesis for levitating small objects, pyrokinesis to ignite targets, and subtle psychic influence to manipulate emotions or seduce others. As a highly skilled martial artist and swordsman, she serves as a deadly enforcer, often employing deception and psychological warfare, which made her a recurring foe for Daredevil, blending physical combat with mental torment in their complex love-hate dynamic.

Over the years, Typhoid Mary has undergone significant developments, including conflicts with heroes like Spider-Man, Deadpool (with whom she had a disturbing romantic entanglement), and Wolverine, as well as appearances in miniseries exploring her fractured psyche. She briefly joined the Initiative program as "Mutant Zero" in a powered suit, temporarily merging her personalities, and has allied with groups like the Hand and the Sisterhood of Mutants. In later stories, she married Wilson Fisk, becoming his second wife, further entrenching her ties to organized crime while highlighting her ongoing struggles with mental illness and identity.