Arrancar Army

The Arrancar Army (破面の軍隊, (アランカル・アーミー), Arankaru Āmī); Japanese for "Army of Ripped Masks") is the military organization of Arrancar and Hollows in Hueco Mundo.

History
In development

Espada
The Espada (十刃, (エスパーダ), Esupāda; Spanish for "Sword", Japanese for "Ten Blades") are the top-ranked Arrancar in the army of Hollow-Shinigami hybrids; they are the most powerful Hollows within the Arrancar Army's ranks, and they are the main rivals of the Gotei 13.

Privaron Espada
The Privaron Espada (十刃落ち (プリバロン・エスパーダ), puribaron esupāda; Spanish for "Deprived Sword", Japanese for "Ten Fallen Blades") 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 Tres Cifras (３ケタ (トレス・シフラス), toresu shifurasu; Japanese for "Three-digit", Spanish for "Three Digits").

Números
The Números (数字持ち（ヌメロス）, Numerosu; Spanish for "Numbers", Japanese for "Number Holders") are the combat experts in the Arrancar Army. The moment they are "reborn" from Hollows into Arrancar, each member of the Arrancar Army is assigned a two-digit number, starting with 11. This number indicates not the order of the Números' strength, but of their birth. Thus, the higher an Arrancar's number, the younger they are. The strongest among the Números can promoted to Espada.

Fracción
Fracción (従属官 (フラシオン), Furashion; Spanish for "Fraction", Japanese for "Subordinate Officers") are Arrancar that serve a specific Espada. As proof of their status, the Espada have the right to select subordinates from among the Números to supervise directly. They can choose one or many Fracción, or even none at all.

Headquarters
Las Noches (虚夜宮 (ラス・ノーチェス), Rasu Nōchesu; Spanish for "The Nights", Japanese for "Hollow Night Palace") is the fortress located in Hueco Mundo and the base of operations of the Arrancar Army. It is a massive fortress which can be seen for miles. It consists of a main building with a domed center surrounded by several large towers and smaller buildings. Atop the dome are five smaller towers, which appear to contain areas such the Espada meeting hall. Like everything else in Hueco Mundo, the main building is colored white.

Due to their immense power, Espada ranked four and above are forbidden from releasing their Zanpakutō within Las Noches. It is also forbidden for any Espada to use a Gran Rey Cero inside Las Noches.

Uniforms
The Arrancar have a common theme for their clothing. Their uniforms consist of a white jacket, black sash, white hakama, black tabi and white zōri that bear an opposing similarity to a Shinigami's zōri; in essence, the uniforms are basically inverted Shinigami uniforms. Arrancar uniforms display more variation than those worn by Shinigami however.