|Head of State||Tier Harribel|
Nelliel Tu Odelschwanck
Baraggan Louisenbairn (formerly)
Sōsuke Aizen (formerly)
|Military Branch||Espada, Privaron Espada, Exequias, Números|
Hueco Mundo (虚圏 (ウェコムンド), Wekomundo; Spanish for "Hollow World", Japanese for "Hollow Sphere") is the domain of Hollows and Arrancar, and a world that lies between the Material World and Soul Society.
In ancient times, before the separation of Soul Society, the Material World, and Hueco Mundo, the universe existed in ambiguity and the cycle of souls in chaos. It remained this way for one hundred million years, until Hollows were introduced to the cycle and began to devour Humans, which slowed the circulation down. Eventually, many of these Hollows cannibalized one another, forming the first Menos. The universe reacted to the creation of such a being and gave way to the Soul King, who destroyed the Menos Grande and allowed the cycle of souls to resume.
Unfortunately, the Soul King's method of destroying Hollows (which very much resembled the Quincy) threw the cycle into further chaos. In response to this, five powerful individuals—those who were the ancestors of the Four Great Noble Families and an unknown fifth—rose in opposition to the Soul King's actions, each with their own motivations. Regardless of their varying motivations, these early nobles ultimately decided to split the world in three: a world of order, a world of implementation, and a paradise of sand for Hollows. But, in order to accomplish their vision, they needed the power of the Soul King.
The Shiba Family ancestor was the only one of the five to speak out against the plan, but they were soundly ignored. The Soul King was captured, hacked up, and his remains were restrained in a crystal. Then, his power, "The Almighty," was used as the keystone to create the three worlds: Soul Society, the Material World, and Hueco Mundo. Meanwhile, the pieces that were gouged out of the Soul King's body fell into the Material World and Soul Society. This became known as Soul Society's "original sin" (原罪, genzai).
Sometime thereafter, Hollow evolution became chaotic. Hollows sought a humanoid form but were unable to do so without a strong will. However, the ancient Hollow, Baraggan Louisenbairn, and a group of Hollows that followed him, learned to evolve beyond the Adjuchas level and became the first Vasto Lorde.
Hueco Mundo is a dimension trapped in an endless night and covered by desert sands. Treelike formations dot the sandy terrain, but these are actually made up of a material resembling quartz. Despite its seemingly lifeless appearance, Hueco Mundo is a thriving dimension full of Hollow lifeforms of all kinds. Though most Hollows feed on Human souls, smaller Hollows can use the extremely dense Reishi in Hueco Mundo's atmosphere to sustain themselves. This high-concentration of ambient Reishi can also improve the fighting abilities of a Quincy.
Access to Hueco Mundo
Hueco Mundo is accessed and left by use of a Garganta (黒腔 (ガルガンタ), Garuganta; Spanish for "Throat", Japanese for "Black Cavity"): a tear between dimensions that can be opened by Hollows and Arrancar.
Since ancient times, Hueco Mundo was governed by a king. The first of these kings was Baraggan Louisenbairn, who was one of the first Vasto Lordes. Thousands of years later, Sōsuke Aizen supplanted Baraggan's rule during his rebellion against Soul Society. However, with the death of Baraggan and the defeat of Aizen, no one was left to rule in Hueco Mundo. Tier Harribel briefly became queen until Hueco Mundo was conquered and occupied by the Wandenreich. After the defeat of the Quincy, Harribel, Grimmjow Jaegerjaquez, and Nelliel Tu Odelschwanck—as the strongest Arrancar in Hueco Mundo—ruled alongside one another.