When Ria was a young girl, she lived in human society where she was cruelly treated for being a deviant (a being who had both human and vampire blood) until she used her powers to escape from her confinement when she awakened to them. She was pursued by the Church without rest, but just when she seemed to lose hope, the Undead Lord appeared and took her into her care.
Grateful to the Undead Lord for saving her life, Ria repayed her by joining the deviant army hoping to someday fight alongside her in saving other deviants from the wrath of the humans. Ultimately, Ria's wish is to be normal, which she invokes for Anhel's enslavement.
Ria possesses the "Ruin's Legis" ability which allows her to switch between human and vampire forms at her own will. While this is not a magical ability, it is a rather unique characteristic that Ria possesses.