A 12th grade student and the prettiest girl in the academy. Comes from the old noble of pure devils, the house of Gremory, a top-class devil who is called a genius nicknamed "Crimson Ruin Princess". Her brother is in fact one of the Yondai-Maou, Lucifer. Both of them possess the power of destruction. She revives Issei as her servant after finding him dead, killed by a fallen-angel and possessing a rare Sacred Gear.
From her mother, Rias has inherited the Bael Clan's Power of Destruction. This power allows her to release energies that can disintegrate matter, both living and inanimate, with relative ease. Opponents who wield sufficiently greater power, however, can shield themselves from this.