Arrancar are a group of Hollows that gained similar powers to that of a Shinigami by removing their masks. The individuals that Aizen turned into Arrancar using the Hōgyoku possess powers far beyond those of previous Arrancar. Especially powerful Arrancar were assigned ten numbers by Sōsuke Aizen and came to be known as the Espada.
Arrancar are the result of Hollows removing their masks. However, an average Hollow removing their mask would not be a problem for the Gotei 13: to hold their own against the Gotei 13, the ones removing their masks would need to be Gillian or stronger. Pseudo-Arrancar have not developed much in the past few decades. Sōsuke Aizen was the first to create a breakthrough; Aizen managed to create a full Arrancar by using the Hōgyoku.
The number that the Arrancar (with numbers 11 and above) have are not the order of their strength, but rather the order of their birth. First, via the Hōgyoku, they are reborn from Hollows into Arrancar. Then, according to the order in which they are born, they were assigned a number, starting with eleven.
Arrancar vs. Hollow
Arrancar and ordinary Hollows differ in several ways:
- Humanoid Form: A Menos usually takes on a Human shape when it becomes an Arrancar. The only ones that will definitely get a 100% Humanoid form are Vasto Lorde-class Menos. For the remaining two levels, there are many who don't get a completely Humanoid form, despite becoming Arrancar. Therefore, the closer one looks to a Hollow, the lower its power of reasoning. There have been Arrancar who have claimed that they gave up their Humanoid forms in order to obtain enormous power. All Arrancar retain a hole in them somewhere, as well as fragments of their Hollow form (in the shape of protrusions and partial masks). A number of Arrancar have tried to conceal the remnants of their past whilst others choose to hide their faces completely to escape unwanted attention. Most also have a colored marking of some sort on their face, although some only gain these markings upon the release of their Zanpakutō (Ex: Nnoitra, Szayelaporro, and Harribel). A few cases that include visible markings without the release of a Zanpakutō include Ulquiorra's tear marks, Sung-Sun's pink dots, the dashes under Grimmjow's eyes, the marking which runs across Nelliel's cheekbones and nose, and the marks on Yammy's cheek bones.
- Physiology: Uryū Ishida theorized that Arrancar share not only the powers of Shinigami, but also their anatomy. During his battle with Cirucci Sanderwicci, he aimed for the area where the Chain of Fate would be located, and upon striking it Cirucci immediately lost not only her release form and mask fragment, but seemingly all traces of her former power.
- Estigma: the pattern on an Arrancar's face. It is potentially the remaining part of a mask and is unique to each individual. The pattern may appear when performing Resurrección for many Arrancar.
- Hole: one of the most distinctive characteristics of an Arrancar is the hole in their body. It is said to represent the lack of a heart that is difficult to fill.
- Zanpakutō: The Arrancar seal the nuclei of their abilities within the form of a sword. It is entirely different from what Shinigami use. When they release their Zanpakutō's seal, they unleash their true power and their true form. The combat efficiency of an Arrancar with a released Zanpakutō is increased several times over. 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, which is activated with a command phrase followed by the name of the sword. An Espada's Resurrección is claimed to be different from that of a normal Arrancar.