Frozen Prison

Frozen Prison (氷結牢獄) is the maximum-security prison where the Great Tomb of Nazarick keeps its prisoners.

Background
The prison is managed by two Area Guardians: Nigredo and Neuronist Painkill. Nigredo was only the Area Guardian of the above-ground portion of the Frozen Prison while Neuronist was the Area Guardian of the underground portion was in charge of this facility located on the 5th Floor.

The Undead King Arc
According to Albedo, the commander of the Slane Theocracy's Sunlight Scripture captured by forces of Nazarick has been incarcerated in the Frozen Prison.

The Bloody Valkyrie Arc
Ainz Ooal Gown and Albedo paid a visit to Nigredo in the Frozen Prison. After briefly alerting the area's spawned creatures they went to Nigredo's room to request her to use her surveillance abilities on locating Shalltear Bloodfallen.

The Pleiades Day Arc
Due to her actions, Nigredo was confined in the Frozen Prison with Pestonya Shortcake Wanko as her cellmate. Later, with permission from Ainz, Yuri Alpha secured their release to assist her in building a Sorcerer Kingdom sponsored orphanage.

The Witch of the Falling Kingdom Arc
An hour after listening to the Floor Guardians' briefings on the war with the Re-Estize Kingdom, Ainz went to the Frozen Prison to have a meeting with Nigredo and Pestonya.

The Half Elf God-kin Arc
When Ainz attempted to contact Albedo after deciding to head to the Elf Country, he learned that at the time she was in the prison.

After Mare Bello Fiore successfully defeated Antilene Heran Fouche and took her prisoner he informed his master Ainz Ooal Gown of the woman’s possible link to Shalltear’s brainwashing. Ainz then transported his party from the Elven Royal Castle back to the Log Cabin so that Aura could carry the prisoner to the Frozen Prison so she could be interrogated by Neuronist. Having been warned about the woman’s formidable strength, Ainz assigned Mare to stand guard with Neuronist.

Afterwards Ainz was present in the interrogation room where Antilene was caged before Neuronist, and the dark elf twins. It was there he learned that the Slane Theocracy was indeed responsible for brainwashing Shalltear, causing him to summon Albedo to inform her that the Sorcerer Kingdom was declaring war on the human nation.

Layout & Features
The Frozen Prison resembles a fairy-tale castle but the interior is anything but magical. Various wraiths and undead lie in wait, hidden from seeing eyes to launch themselves at trespassers. Located in the fifth floor of Nazarick where the entire terrain is a frozen wasteland, escape from this stronghold is impossible.


 * Room of Nigredo: The cell where Nigredo, Overseer Guardian Albedo's sister, is kept in confinement. The entrance to her chamber is disguised as a painting of a mother cuddling her baby.
 * Room of Truth (Pain is not to tell): Neuronist Painkill's personal place of office. In other words, where Neuronist and her Torturers process freshly caught captives for interrogation. It's filled with a number of horrendous torture contraptions and equipment.

Trivia

 * It is said that the temperature inside the prison is even lower than that of the Arctic world of the 5th Floor.
 * Cocytus is known to be training in his home at the Frozen Prison, and was visited by Shalltear.
 * In Overlord: The Undead Oh!, the Frozen Prison resembles an icy mansion.
 * In Mass for the Dead, the function for Frozen Prison, save for Nigredo's cell, had to be shut down to conserve resources. Hence, Neuronist's torture facility was relocated to the floors under Shalltear Bloodfallen's control.
 * In OVERLORD -ESCAPE FROM NAZARICK-, the castle makes a visual appearance in the background and setting.
 * Also inside the Frozen Prison is a room containing three pictures each depicting an image of a decapitated girl, which was placed there by Tabula Smaragdina as a gimmick. Supposedly according to urban myth bad luck or a death curse comes in threes.
 * For a time the children that Pestonya and Nigredo rescued from death after the Demonic Disturbance were kept and cared here while the two women were in confinement. Pestonya used her magic to summon Archangel Flames to help care for the children. They were also secretly helped by others such as Clavu, Shihoutu Tokitu, Cocytus, the Frost Virgins and Neuronist Painkill.
 * In Mass for the Dead, Succulent was imprisoned in the Frozen Prison so that he would not interfere with Lupusregina Beta and CZ2128 Delta's worker identities in New Six Arms.