An arrancar (sometimes written allankar or arankaru) is a hollow that has removed its mask and gained shinigami powers. The name arrancar is a Spanish verb meaning "to remove" or "to rip off," a reference to an arrancar's removal of its hollow mask. In the manga, it is written as arankaru (lit. rip mask) but has no native Japanese pronunciation, instead using the katakana for arankaru.
Few hollows have the potential to remove their masks normally, and even if they manage it the change is not significant. Sōsuke Aizen is able to artificially create arrancar with the Orb of Distortion, which also unlocks much more of their potential than a natural transformation would. The process of turning a hollow into an arrancar is called shinigamification.
Arrancar and ordinary hollows differ in two ways: the location of their holes and the near-total disappearance of their masks. When hollows become arrancar, the chances of them retaining a humanoid form increase with their intelligence; only vasto lorde-class arrancar will definitely assume a humanoid form. If powerful enough, an arrancar can seal his or her excess power into the form of a zanpakutō. Unlike with shinigami, this zanpakutō is by no means sentient. It is simply the hollow's true form sealed into a sword. Therefore, an arrancar's release of their zanpakutō is merely a temporary restoration of their former selves. An arrancar release is called resurrección (Spanish for "resurrection"wink. Arrancar do not have a known second release.
Those arrancar under Aizen's command also have a standard theme for their clothing. Their uniforms consist of a white jacket, black sash, white hakama, and black socks with white sandals; in essence, the uniforms are basically inverted shinigami uniforms.
How I look: (Most of the time)
Personal Info: Aaroniero was a gillian, the weakest class of menos, before becoming an arrancar. What has kept him from being a simple Número is his ability to absorb other hollows and gain their power. Having absorbed 33,650 hollows thus far, his power is great enough to allow him a place in Aizen's Espada. His clothing is unusual for arrancar; he has a frilly white coat, with puffs at the end of the sleeves. He usually covers his face with a white mask covered in holes while in the light.
Due to his ability to absorb other hollows, Aaroniero can take the form of anyone he has consumed, though his clothing remains the same. He uses this ability to hide his true appearance. The weakness of this power is sunlight, which nullifies it on contact and reveals Aaroniero's true form. Aaroniero's true form is still humanoid, but with an odd "head". In place of a normal head, he has a large, glass capsule filled with red liquid and two floating heads. Both heads have the number 9 tattooed on their face: the lower head has the tattoo on his left cheek and the upper head has it over his right eye. The two heads tend to talk in tandem when revealed, giving the effect of two people speaking at once. Aaroniero doesn't care for insults about his head, telling Rukia that he has grown tired of hearing other people's opinions about it.
Powers: Aaroniero has the ability to completely absorb other hollows, merging the sum total of their power with his own. This merger gives him access to their spiritual form, memories, and even their unique abilities. Aaroniero can manifest these powers at will, but not all at once unless he unseals his zanpakutō. Aaroniero also possesses the shinigami abilities of Kaien Shiba, having consumed Metastacia, the hollow who merged with Kaien. Like his shapeshifting abilities, manifesting his powers only works when he is not exposed to sunlight. Ulquiorra Schiffer explains to Ichigo Kurosaki that Aaroniero also has the ability to broadcast information on whatever he is currently seeing or experiencing to other arrancar; this ability is the reason why everyone in Hueco Mundo (aside from the intruders) knows that he and Rukia defeated each other.
Zanpaktou: Glotonería (喰虚, lit. eating hollow, Spanish for gluttony) is Aaroniero's zanpakutō. It is activated by the command "devour" (喰い尽くせ, kuitsukuse?). When sealed, Aaroniero can 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. His absorption ability also allows him to perfectly mimic the accompanying battle styles of those powers.
When released, it turns Aaroniero into a huge, blob-like mass, giving him access to the full range 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.