Aaroniero Arruruerie is the ninth Espada in Aizen's army, and the last of Aizen's original team of Espada.
Aaroniero originally took the form of Kaien Shiba, during his encounter with Rukia Kuchiki. He later revealed that behind his mask was a helmet containing two floating heads, on both of which was his Espada tattoo. Each of the heads contains a part of his mask remnants, and his hollow hole whereabouts are unknown.
Aaroniero's outfit is very different from that of a normal arrancar, with a large, frilly collar. Aaroniero also sports a white mask, which is used to conceal his true face.