|Base of Operations||Las Noches|
Aaroniero usually covers his face with an elongated white mask covered with eight holes while in the light. In place of a normal head, he has a large, glass cylindrical capsule filled with red liquid and two small, floating Hollow heads. The two heads are both tattooed with the number 9 and tend to talk in tandem when revealed; the upper head speaks with a deep voice while the other speaks in a high-pitched, child-like voice. The heads appear to have a level of individuality.His outfit, like that of most Espada, is customized; he wears a dress garb that covers his entire body as opposed to the normal jacket and hakama. He also wears a frilly noble's coat that acts as his replacement jacket and a single white glove. The remains of his Hollow mask fragments are on both of his heads, the upper head having three-quarters of his head covered with the mask, and the lower head covering only half of it. His Hollow hole is located in the left thigh area, though this has never been seen.
Aaroniero's personality is difficult to distinguish, but he seems to be rather arrogant, like most Arrancar, and takes sadistic delight in devouring his enemies and/or messing with their psyche. He also expresses a degree of pride in his ability to "keep evolving".
Aaroniero was a Gillian, the weakest class of Menos, before becoming an Arrancar, and the last of the first-generation Espada. At some point in the past, Aaroniero gained the powers of former Shinigami lieutenant Kaien Shiba by absorbing Metastacia, the Hollow who killed and fused with Kaien. By doing this, Aaroniero was able to gain not only Metastacia's power to fuse with others but Kaien Shiba's powers and abilities as well as his Zanpakuto.
- Aaroniero's Aspect of Death is Greed.