After losing her family to a Yoma attack, Priscilla decided to fight all she considered evil in the world. After joining the Organization, she quickly rose to rank #2, and even then she was said to still hold more powers, perhaps holding more potential than any other Claymore before her. Like Teresa, Priscilla had the ability to fight with great power even without using her Youki, thus making her a dangerous opponent for anyone relying on reading the flow of Youki.
Priscilla was one of the four Claymores sent to execute Teresa when she strayed from the organization, but she ended up awakening and kills Teresa when she's off guard. She's one of the most fearsome Awakened Beings.
