She appears to be a girl that wears a black cloak, underneath the black cloak shows her long mechanical arms, she's missing the lower half of her body, she has no legs and feet.
Her legs and lower half was lost by a 'Train Accident'
She has a long tail that ends with a long sharp blade.
She wears a black sailor outfit, she has sharp teeth and white short hair.

She doesn't remember what made her into this killing machine, or how she's got her tail, but she's not ALWAYS cruel.