Little is known about the origins of Lady Satanus. Against her better judgement, she joined the Sworn to avenge her brother Thanatos' murder and proved to be immensely powerful. Though cold, aloof and with an air of superiority, she has an affection for humankind. She continues to fight by the Sworn's side because she finds their antics amusing.
Left to her own devices, she lives a life of luxury and divides her time between indulging her sensual appetities, hunting corrupt human souls.