Aaroniero Arruruerie

is an Arrancar in Sōsuke Aizen's army, and the novena (9th) Espada.

Appearance
He usually covers his face with a white mask covered with eight holes while in the light. In place of a normal head, he has a large, glass capsule filled with red liquid and two floating heads. The two heads are both tattooed with the number 9 and tend to talk in tandem when revealed, giving the effect of two people speaking in turn. The upper head speaks with a deep voice while the other speaks in a high-pitched, child-like voice, and appear to have a level of individuality. His outfit like 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 nobles' coat that acts as his replacement jacket and two white gentleman's gloves.

History
Aaroniero was a gillian, the weakest class of Menos, before becoming an arrancar, and the last of the first-generation Espada. His original number wasn't mentioned (it is implied to have been quite high), but it is possible he was demoted to a lower number in accordance with the arrival of more powerful 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 Zanpakutō.

Arrancar Arc
Aaroniero is briefly seen as a shadowy figure for some short periods of time in the Arrancar Arc, such as when Ulquiorra Schiffer reports to Aizen about what he and Yammy had encountered. He is seen the second time when Aizen is creating Wonderwice Margera. He is just seen standing there but this time only half of his body is covered in shadow.

Hueco Mundo Arc
He next appears, this time with his white mask on, when the Espada are gathered by Aizen about Ichigo Kurosaki, Yasutora Sado and Uryu Ishida entering Hueco Mundo to save Orihime Inoue. He sits between Halibel and Yammy and complains about the intruders along with Barragan Luisenbarn, Szayel Aporro Granz, Yammy and Nnoitra Jiruga. He is also heard talking for the first time and he has two voices: one for each head.

Aaroniero later meets up with Rukia Kuchiki and tells her to follow him and as she does, he brings her into a large dark room (his room), and takes off his mask just to show Rukia the face of Kaien Shiba. He claims the reason he led her there was because Aizen could see everything in the "sunlight" of Las Noches. Aaroniero deceives Rukia into thinking he truly is Kaien, explaining that Metastacia was built in such a way that it would return to Hueco Mundo when destroyed. Having been merged together at the time of its death, the two were sent back as one merged entity. Rukia believes its actually him, so Aaroniero plays along with it.

He goes on to explain that Kaien is actually the dominant one, while the other arrancar believe the hollow is in control. However, Aaroniero's erratic behavior betrays his claim: he claims to be Rukia's friend and then strikes her, suggests that Rukia kill her friends in order to earn his forgiveness, and alternates between being serious and joking almost instantly. This leads Rukia to attack him, convinced that the real Kaien would not act in such a manner.

Because Aaroniero possesses all of Kaien's memories, he knows all of Rukia's techniques, as Kaien was Rukia's superior officer and supervised her training. Rukia eventually concludes that everything Aaroniero said was a lie, and notices him running from sunlight. She uses kidō to restrain him and then blow a hole in the wall, forcing him to remain in the sunlight. This reveals Aaroniero's true face. With this, Rukia is finally given definitive evidence that Aaroniero is not Kaien. Assured that she won't have to hold back anymore, and confident that she has unveiled all of Aaroniero's transformation abilities, Rukia appears to gain the upper hand.

At this point, however, Aaroniero finally chooses to display his true abilities as a "hollow eater." He explains the truth behind the acquisition of Kaien's powers, and reveals that Rukia is indeed fighting Kaien's real spirit body. The news tears at Rukia: she had always reasoned that by killing Kaien, she had saved him from the enemy. The realization of her failure renders Rukia dejected and unable to lift her sword against Kaien's body. Aaroniero releases his zanpakutō and impales Rukia on the end of Nejibana.

Spurred on by her memories of Kaien, she uses the last of her strength to perform her Shikai's third dance, impaling Aaroniero through his top face and shattering the container that sits in place of his head. The bottom face dies screaming in agony while feeling betrayed by Aizen's promise that he would never be in pain again, while the top face curses one last time before spliting in half.

Powers & Abilities
Aaroniero is unique among Arrancar (and all Hollow) due to the fact that he has two Zanpakutō, one of them being a Shinigami 's Zanpakutō (it is not known whether it retains the soul of the Zanpakutō, since a Zanpakutō spirit is part of the Shinigami's soul), and can thus perform Shikai. This is due to Metastacia's ability.

Hollow Absorption: While all Hollows can cannibalize each other to gain power, Aaroniero has the ability to completely absorb other Hollows, merging not only their extra power with his own but also gaining their individual abilities.


 * Aspect Manifestation: Once a hollow is absorbed in this fashion, Aaroniero can manifest any aspect of them at will, including their physical form. It is for this reason that Aaroniero, despite his gillian status, was able to become an Espada. Through an unusual series of events, he also absorbs the Shinigami abilities of Kaien Shiba by eating Metastacia.


 * The weakness of this power is sunlight, which nullifies it on contact and reveals Aaroniero's true form.




 * Shikai: Its shikai command is . Nejibana's shikai is represented as a cross between a trident and a ji (a Chinese halberd) with a crystalline appearance that has the ability to manipulate water. Like the ji, it bears a horsehair tassel, although it is blue instead of the traditional red; similarly the two side blades are straight with concave edges as opposed to the usual crescent blade.


 * Shikai Special Ability: During Rukia's battle with Aaroniero, Nejibana's abilities are shown with the ability to use the shockwaves it creates in conjunction with trident attacks to "crush and split the enemy in two." Kaien's techniques and form are also revealed during the battle, and are described by Rukia as "a trident technique reminiscent of dancing."

Broadcasted Sight: Aaroniero also has the ability to broadcast information of whatever he is currently seeing or experiencing to other arrancar, which he does prior to his death at the hands of Rukia.

Zanpakutō
. By chance Aaroniero's Zanpakutō takes the form of former Shinigami lieutenant Kaien Shiba's unreleased Nejibana. However his Zanpakutō may also be a deformed arm-like appendage with many sprouting tentacles that is concealed in his left hand under his glove.


 * Resurrección: It is activated by the command . When released, it turns Aaroniero's lower body into a huge, blob-like mass resembling an incredibly bloated cartoonish octopus, with dozens of stubby tentacles and mouth-like mask pieces (In the anime the blob mass is colored purplish).


 * Resurrección Special Ability:


 * Manifest Absorbed Power: When sealed it allows Aaroniero to manifest any power he has absorbed through his Zanpakutō, morphing it into a perfect approximation of the one he absorbed, as he does with Kaien's Nejibana. When released it allows Aaroniero full access of his absorbed abilities. He can still manifest the powers of those he has absorbed in this form, but has no limit to the total number.


 * Mimic Battle Style: His absorption ability also allows him to perfectly mimic the accompanying battle styles of those powers.

Trivia

 * His name like Grimmjow's and Nnoitra's was also a hot debate about his original name Arroniro being changed to Aaroniero; as well as his last name Arleri changed to Arruruerie.
 * His name stems from that of a Finnish furniture designer named Eero Aarnio.
 * He is also the only arrancar with both a shikai and resurrección, although the former was acquired from consuming a shinigami.