Arrancar

An 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. Following the retrieval of the Hogyoku and Aizen's emergence into Hueco Mundo, the Arrancar have become the main antagonists of the series, especially the Espada.

Overview
Few Hollows have the potential to remove their masks naturally, and even if they manage to do so, the change may not be significant. Sōsuke Aizen is able to artificially create Arrancar with the Hōgyoku, 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 several ways:


 * Arrancar assume a humanoid body, as opposed to the animal-like or monstrous forms seen from Hollows. Upon becoming an Arrancar, the chances of a Hollow retaining a humanoid form increase with their intelligence; only Vasto Lorde-class Menos will definitely assume a humanoid form. This new form will retain remnants of their past selves, like fragments of their removed masks and a Hollow hole. While some Arrancar prefer to conceal these remnants (such as Nnoitra and Halibel), others (like Aaroniero) hide their faces completely to escape unwanted attention.


 * Arrancar can gain a Zanpakutō. Unlike with Shinigami, this Zanpakutō is not sentient, but simply their "true" Hollow form sealed into a sword. Therefore, an Arrancar's release of their Zanpakutō is merely a temporary restoration to their former selves, granting them any powers their Hollow form possesses. The act of release is called Resurrección (Spanish for "resurrection"), which is activated with a command phrase followed by the name of the sword. The Resurrección of Espada-level Arrancar releases enough power to be comparable to a Shinigami's Bankai. Few Arrancar do not have a Zanpakutō, being too weak to seal their excess power into a blade, while others prefer to have it constantly released, as with Iceringer and Demōra.

The Arrancar under Aizen's command have a standard theme for their clothing. Their uniforms consist of a white jacket, black sash, white hakama, and black and white shoes that resemble sandals; in essence, the uniforms are basically inverted Shinigami uniforms.

Arrancar ranks
are the top-ranked Arrancar in Aizen's army. The Espada at the time of the group's introduction consists of nine males and one female. Each Espada member is chosen for their superior combat ability and then assigned a number from 1 to 10 (with 1 being the strongest) that indicates their rank and relative power level, which is tattooed somewhere on their body (Grimmjow's is on his lower back, for instance). The Espada are given control over the Números and are regarded as the strongest Arrancar in existence. Similar to the power gap between captains and lieutenants in the Gotei 13, the strength of the Espada far surpasses that of the average Número. As Aaroniero Arruruerie notes, all of the Espada except him were at least Adjuchas-class Menos before becoming Arrancar.


 * are former Espada who have officially lost their rank and are assigned a three-digit number. Being former Espada, they are far stronger than the normal Números. They reside in the part of Las Noches called Tres Cifras, which translates literally from Spanish as "three digits". As mentioned by Dordonii, these former "naturally created" Espada were rendered obsolete after Aizen began artificially creating Arrancar to meet his own standards. It is also noted that Aaroniero Arruruerie was one of the original Espada, but his original number was not mentioned since it is possible he was demoted to a lower number in accordance to the arrival of more powerful Espada.

are the combat specialists. They are assigned a two digit number at birth from 11 to 99 to indicate their age (Número 11 is the oldest, Número 99 is the youngest). The basic Número uniform consists of a white-collared jacket and robes held with a black sash. However, the uniform is customizable, giving each Número a sense of individuality. The fighting ability of Números is thought to be superior to all other Arrancar, except for the Espada (current and former).


 * are a subsection of the Números that directly serve a specific Espada. The number of Fracción for any given Espada varies: Stark and Nnoitra Jiruga would seem to have just one, while Szayel Aporro Granz has at least a dozen. There are a few Espada that apparently prefer to fight alone, such as Yammy, Zommari Leroux, Ulquiorra Schiffer and Aaroniero, seem to have chose not to have any Fracción under their command.

are Arrancar that are part of the execution division, apparently charged with termination of intruders and rebels. They are the equivalent of Soul Society's Onmitsukidō. Their captain is the bull-headed Rudobōn.

Las Noches
Aizen's Arrancar reside in Las Noches, a massive, white-colored fortress in Hueco Mundo.

Powers
Like Shinigami, Arrancar have a multitude of combat skills and abilities, some of which are similar to those of the former, and some of which are variations on ordinary Hollow powers.


 * is an Arrancar alternative to Cero. The technique hardens the user's Spiritual Pressure and fires it like a bullet from their fist. It is seriously weaker than a normal cero, it moves about twenty times faster and can be fired at a much higher rate, but the damage is much the same.


 * Cero are high-powered energy blasts that can be fired from various body parts, such as mouth, tongue, hand or fingers. Only Menos, Arrancar, and the Vizards have so far been shown to use Cero attacks, and it appears that stronger entities can use it more efficiently. Various Arrancar and Hollow characters display variants of the technique, such as the Espada-exclusive Gran Rey Cero, as well as Cero Sincrético performed by Pesche Guatische and Dondochakka Bilstin.


 * is how Arrancar and Menos-class Hollows move to and from Hueco Mundo. Kaname Tōsen and Kisuke Urahara have also demonstrated the ability to use the technique. It literally tears open the dimensional fabric separating the worlds, revealing a tunnel of whirling, torrential energy that must be focused and solidified to create a discernible pathway.


 * refers to the hardened skin of the Arrancar, which is a result of their compressed spiritual power. While their skin is strong enough to block even released Zanpakutō bare-handed, it is by no means impenetrable. Stronger Arrancar have proportionally stronger skin.


 * fields are used to rescue fellow Hollows. Only the Gillian-class Menos have shown the ability to use it. Negación fields surround a target in a square beam of light that isolates the target from the dimension they are currently in, making it impossible to harm them. The field then pulls the target towards the menos that created the field. Espada have a special cube-shaped device called meant to simulate Negación fields, which are used to punish their subordinates if necessary.  The cube, when used on a subject, traps them in an alternate dimension from which there is no escape; however, this assumes it is being used as intended. More powerful Arrancar, namely the Espada themselves, can escape given enough time.


 * is the Arrancar equivalent of the Shinigami ability to sense Spiritual Pressure. It functions similar to a sonar.


 * is the Arrancar equivalent of the Shinigami Flash Steps and the Quincy Hirenkyaku; it allows the user to travel at incredibly high speeds for short distances. Use of Sonído is punctuated by a brief static sound, in contrast to the "swish" sound caused by Flash Steps.

Name Origins
The nomenclature for several of the Arrancar originate from real-world architects or designers. The following characters have their namesakes shown below, as well as the profession the real-world counterpart is notable for.


 * Stark - Philippe Starck (French Designer)
 * Barragan - Luis Barragan (Architect)
 * Halibel - Harry Bell Measures (Architect)
 * Ulquiorra - Patricia Urquiola (Architect) and Father Hubert Schiffer (he was a survivor of the bomb of Hiroshima, Tite Kubo is from Hiroshima).
 * Nnoitra - Richard Neutra (Architect) [In Japanese Nnoitra is pronounced Noitra very quickly, it sounds like Neutra.]
 * Grimmjow - Nicholas Grimmshaw (Architect)
 * Szayel Aporro - Alejandro Zaera Polo. (Architect)
 * Aaroniero - Eero Aarnio (Designer furniture)
 * Luppi - Italo Lupi (Architect)
 * Dordonii - Rodolfo Dordoni (Architect)
 * Gantenbainne - (Architect)
 * Yylfordt - Rabbi Yeruchem Eilfort
 * Tesla - Nikola Tesla (Inventor, Mechanical and Electrical Engineer)
 * Pesche - Gaetano Pesce (Architect and Designer)
 * Bawabawa - Geoffrey Bawa (Architect)
 * Cuuhlhourne - Menno van Coehourn (17th century Dutch military architect and chief rival of the Marquis de Vauban)