in death's other kingdom
After Aizen leaves Soul Society, an investigation is launched to find out what his true goal is. It's discovered that Aizen seeks to create the ou ken, or royal key,
a device which will allow him to enter the dimension where the "Spirit King" of Soul Society resides.
Gaining access to this dimension will allow Aizen to "stand in heaven," as he said when he left Soul Society. In order to create the key, Aizen needs one million modsouls and one
mile of land "rich with souls." And that land, Aizen determined, is Karakura Town, the home of Ichigo and the other human protagonists.
It's also revealed that Aizen has set up an empire of sorts in Hueco Mundo, or "Hollow World," the desert-like world where Hollows reside. Itís unclear just how long
Aizen has been ruling over this world, but by the time Ichigo and friends return from Soul Society, he has quite the army under his command. At some point while he was still a
Captain, Aizen had challenged the king of Hueco Mundo, Baraggan Luisenbarn, and won, gaining control over that world.
Aizen resides in a palace-like building called Los Noches, where he has fashioned himself into an emperor-like figure. His appearance has changed dramatically
from the one he had in Soul Society; the bespectacled, scholarly-looking figure has been replaced by a regal-looking man, complete with a throne and robes. And terrible hair,
but thatís beside the point. What does matter is the fact that
His army consists of countless Arrancar, Hollows who have removed their masks to become humanoid Shinigami-Hollow hybrids. With the aid of the Hougyoku,
Aizen managed to create incredibly powerful Arrancar from the strongest classes of Hollows. His ten strongest warriors are known as the Espada.
The majority of the Arrancar that make up Aizen's forces display total loyalty to their leader, some through intimidation, others through admiration. It's explained that Hollows
are creatures born from fear, and thus many choose to respect and follow Aizen, a man who demonstrates no fear.
After determining Aizen's plans, Soul Society officials believe that the Hougyoku will take four months to mature, and spend that time preparing for war. Yet things get
complicated when Orihime is kidnapped and taken to Hueco Mundo under Aizenís orders. Once Ichigo and his friends receive the news that
Orihime has been kidnapped, they decide that there will be no waiting around. Ichigo, Ishida, and Chad make their way to Hueco Mundo with Urahara's help, eventually
followed by Rukia and Renji. Aizen explains that he has taken an interest in Orihimeís special powers, the Shun Shun Rikka, especially her ability to "reject" matter, with
which he hopes to awaken the Hougyoku. After entering Hueco Mundo, Ichigo and co. begin to battle their way through Aizen's legion of Arrancar. Eventually, a number of
Shinigami arrive to help, including four Captains: Byakuya, Kenpachi, the Fourth Division's Unohana Retsu, and the Twelfth Division's Kurotsuchi Mayuri.
Ichigo eventually manages to reach Orihime, and with a little help from Kenpachi it looks as if But Aizen reveals that his plans for Orihime were not what he initially explained
them to be. Instead, he brought her to Soul Society in order to lure its forces there. Soul Society knew just how unique her powers were, and making them turn their focus to
Hueco Mundo rather than their own defenses was part of Aizenís plan. He also was able to lure Ichigo and the other humans to Hueco Mundo. He plans to trap Orihimeís
rescuers in Hueco Mundo as he leaves to destroy Karakura town. But Kenpachi reveals that the Gotei 13 have been planning their defense all along: Karakura town and its
inhabitants have been transferred to Soul Society, while the rest of the Captains and Vice Captains lay waiting for Aizen where it used to be. And so the war between Soul Society and Aizen's forces
officially begins, with Aizen explaining that he can just destroy the Captains there to create the key, rather than Karakura town.