Milady, a 23-year-old English operative for Cardinal Richelieu, executes covert missions across Paris with chilling precision. Her arsenal blends seductive charm, implied arcane talents, and a specialized ultrasonic whistle enabling absolute command over animals. Fueled by undisclosed grievances against the crown and nobility, she acts as Richelieu's key enforcer alongside Rochefort, targeting Queen Anne's faction through morally murky schemes. Her espionage employs a surveillance parrot and a pet monkey named Pepe, who receives notably tender treatment compared to other creatures she manipulates. Despite frequent disguises—including a signature domino mask—her vivid green hair and eyes often betray her identity.

Ruthlessly pragmatic, she engineers Constance Bonacieux’s kidnappings, crafts lethal traps involving drowning and fire for foes, and stalks d'Artagnan relentlessly during his English mission. Adept with daggers, she maintains elaborate contingencies: her monkey administers an antidote after she feigns death via poison, allowing undetected resumption of operations.

Her allegiance shifts during the Iron Mask conspiracy, aligning with the masked mastermind and his enforcer Manson. They plot to replace Louis XIII with his twin Philippe, positioning Milady as the imposter king’s advisor. She co-directs military tactics, deploying cannon-fodder decoys during the fortress siege while attempting to flee with plundered treasures.

Isolated amid the conspiracy’s collapse, Milady confronts impending doom with rare vulnerability. Abandoned by allies, she whispers a prayer for divine mercy—a stark departure from her detached ruthlessness—marking her final act after years of influence within Richelieu’s web and the Iron Mask’s cabal.