He needed the medallion and blood of Sparda (possessed by Dante and Vergil) and also the blood of the priestess that Sparda sacrificed the seal the tower which Lady, as the descendant of that priestess, possesses. He reveals his true identity, and disarms them, and proceeds to explain that he manipulated all of them into fighting there, since they are keys to opening the way to the demon world.

The three of them are ambushed by Arkham, in his alter-ego Jester.

Lady finds Vergil fighting his brother and joins in the fight. He then seemingly dies, leaving Lady weeping over his body and swearing revenge on Vergil. He tells Lady that he was manipulated by a demon into killing his wife, and blames Vergil. She explains that Arkham is her father, and that it was her duty as his daughter to kill him. Lady flies into a rage and shoots at him, only to have him evade and counter every shot. Angry, she asks if he killed him, to which he only responds 'So what if I did?'. She eventually finds her father, seemingly dead, with Dante standing over him. Dante eventually leaves her to fight the demons on her own. Dante emerges from one of its eyes, and the two talk briefly before being attacked by demons. Lady presses on, and barely survives the Leviathan almost falling on her. She jams the blade attached to her canon into the wall of the tower to keep from falling, and when Dante yells at her for shooting him, she shoots at him again, only for him to catch the bullet with his teeth and walk away. She repays him by shooting him in the head, causing him to drop her. He manages to toss her off of the tower, but she is saved by Dante who grabs her ankle as she is falling. When approaching the top, she encounters her father, and tries to kill him. Lady enters the hole and continues to make her way up the tower, choosing a different path up than Dante.

She fires a missile at him, but he simply rides it like a skateboard, changing its trajectory into the wall. On her climb, she encounters Dante, Vergil's twin brother, who has come to stop his twin and Arkham from opening a portal to the demon world. When her father and the half-human son of Sparda Vergil, raise Temen-ni-gru, Lady attempts to infiltrate it to kill her father, manually climbing it. She swears to hunt every last demon to extinction. She developed a blinding hatred for her father, and for all demons, whom she blamed for corrupting her father. At some point, Arkham killed her mother for reasons unknown to her, leading her to abandon the name he gave her. Lady was born as Mary to Arkham and an Kalina Ann.

Devil may cry 5 lady