Madame Marciano is a high-ranking official of the Syndicate "Guild" that operates above the law which she broke off from to form another syndicate named "Criminal Guild" not soon after the story started when her motives were questioned by "Guild" members. Untouched by investigators, she commands the 12 Sisters, a squad of hitwomen made up of her robotic "daughters." Marciano is a cold woman that does not seem to care for the Sisters' well-being. She is also the one responsible for the death of the "pirate king" Bruce 3 years before the story took place.
It is revealed in the last episode that Marciano was once a Coyote many years ago and may have known Mister then, but joined the Syndicate"Guild" after an injury made her unable to have any children.