Black Capsule

Black Capsule is the residence of Kyouhukou.

Background
The Black Capsule is the one place where Kyouhukou often resides with his cockroaches. It is a place that appears dangerous for living beings such as humans where they are physically and mentally harmed by cockroaches. One account of this happening was when where a victim's organs were being constantly devoured from the inside by cockroaches. If there are no victims to prey on, cockroaches often cannibalize themselves in the meantime, eating each other to fulfill their appetite.

According to the author Maruyama, the roach pit itself has a very large circumference. Of the 1500 people who invaded the Great Tomb of Nazarick underground, dozens are said to have died there carelessly. They didn't judge the range of their magic accurately and killed dozens of their compacted comrades, others could not endure it and were forced to log out.

The Search for Hamsuke Arc
According to Mare Bello Fiore, when he uses [Detect Life] on the 2nd Floor of Nazarick, he'll get too many returns due to the many cockroach lifeforms found within the Black Capsule. Aura thought the cockroaches should all be in the same area, believing that they won't come out or anything. However, Mare thinks otherwise, seeing that the Black Capsule might have spilled out. Mare and the female Floor Guardians (Aura, Albedo, and Shalltear) were gathered together on the 2nd Floor, having entered the Black Capsule where Hamsuke was apparently residing.

The Two Leaders Arc
While on break, one of the female Floor Guardians noted how the cockroaches in the Black Capsule will be crawling in their clothing all the time when visiting it. Apparently, Entoma Vasilissa Zeta visits the Black Capsule from time to time. Entoma calls the Black Capsule her "snack room" which disgusted Shalltear.

The Men in the Kingdom Arc
When Hilma Cygnaeus was capture by Mare and sent to the tomb, the place she was put in is none other than the Black Capsule where she undergoes a form of baptism to make her obedient and loyal to Nazarick's cause. The rest of the higher-ups in Eight Fingers were also brought over to the Black Capsule for the same treatment as Hilma.

The Invaders of the Large Tomb Arc
After invading the Great Tomb of Nazarick, Gringham and his thief companion ended up getting caught in a magic trap which teleported him into the Black Capsule where he soon lost his life by the hands of Kyouhukou and his vast army of cockroaches.

The Witch of the Falling Kingdom Arc
Before Cocco Doll could work properly under Nazarick's rules and regulations, he was taken by Shalltear via [Gate] to the Black Capsule for baptism in preparation for the job that awaits him after this.

Layout
The room is full of cockroaches and seems to be vastly cover in pitch darkness that not even victims of this area are able to perceive any glimpse of light from, leaving them almost feeling fearfully lost and confused in the process. The room is said to be filled with cockroaches of all different shapes and sizes, and they crawl on top of each other. The smallest cockroaches were only the size of the victim's fingertip while the biggest ones were over a meter long.

There is no trace of light to illuminate this entire area. Amidst the endless darkness without light lies a very huge amount of cockroaches all spread out around and throughout the area. The ceiling of the area for example, is covered with cockroaches. It can be described as a large swamp of cockroaches filling the area entirely. When the victims find themselves in this area, their bodies will continue slowly sinking into the sea of cockroaches until it stops somewhere within their waist. In other words, the victim can appear submerge up to their waist in cockroaches. The room is said to have been far wider than 15 meters as using the Glow Stick to illuminate the area is not nearly enough to show everything in sight. Emerging from within the cesspit/cesspool of cockroaches is Kyouhukou himself who can manipulate the size of his own form from smallest to largest due to the Minimum class.

In this area, Kyouhukou can manipulate a tsunami-type tidal wave of cockroaches at the victims who are surrounded by these insects to consume them. Weapons were deemed useless in dealing with a swarm of tiny insects like cockroaches as it will be hit and miss. The victims are drowned in the ocean of cockroaches to the point that they will attempt to swim and flail for their life, however, with parts of their movement restricted as the insects weigh them down along the way. In the end, over the course of time, they will be engulfed by the excessive amount of cockroaches, having already squirmed their way into every part of the victims' body, including their mouth, throat, stomach, and ears while infiltrating through their clothing like their armor as well. This in turn, while the victims are writhing in pain, their body being eaten alive, and unable to make any further movement such as screaming.

At the same time, it will also allow the cockroaches to chew and bite the flesh of the victims' bodies from the inside and outside simultaneously.

Trivia

 * Although Shalltear Bloodfallen holds control over the 2nd Floor, she happens to bear a dislike for one of the areas within her territory, particularly the Black Capsule.
 * Players on 2channel who had invaded Nazarick before, considered how ridiculous Black Capsule was.
 * In the Web Novel, characters with female exterior are forcibly teleported into this roach pit.