Central Great Underground Prison

Shin'ōchikadaikangoku
Kanji	真央地下大監獄
English	Central Great Underground Prison
Location Statistics
Type	Prison
Located In	Under the 1st Division Barracks
Controlled By	Central 46
Primary Function	Imprisonment of criminal Shinigami
First Appearance
Manga	Chapter 523

The Central Great Underground Prison (真央地下大監獄, Shin'ōchikadaikangoku) is an underground prison where Shinigami who broke the laws of Soul Society are sentenced to.

Overview

The Central Great Underground Prison consists of eight levels, in which the Central 46 decides which the criminal Shinigami would be confined, depending on the severity of his or her crimes. The prison is located underneath the barracks of the First Division.

Known Levels

3rd Level: Shugo

Shugo (衆合, Samghata) is the third level of the underground prison and reserved for those who used forbidden Kidō techniques. Tessai Tsukabishi was to be given a life sentence in this level for using the forbidden Kidō spells Jikanteishi and Kūkanten'i.

8th Level: Muken

Muken (無間, Avici) is the eighth and final level of the underground prison. Sōsuke Aizen was sentenced to 18,800 years in this level for high acts of treason and a long list of other crimes. His outburst during his trial raised the sentencing to 20,000 years.

Muken is a voided space completely sealed off from the outside world, aside from the main tower that serves as the entrance and exit. The realm stretches on infinitely. Under normal circumstances, non-criminals are not permitted entrance, but Retsu Unohana managed to gain permission from Captain-Commander Shunsui Kyōraku to use the location as a battlefield to train Kenpachi Zaraki in Zanjutsu.

When Kyōraku went to visit Aizen in request for his assistance against the Wandenreich, he had the key to the Muken sealed into his chest. Should he be killed, the gates to the outside world would be sealed off, preventing Aizen's escape. Aizen himself is bound by seals in the form of black straps, which could be undone by 19 keyholes on the ground; Kyōraku was given permission to use up to three.