Khangba Marwu

Khangba Marwu, also known as "The Vault", was a large underground Imperial prison complex that was overseen by the they Adeptus Custodes during the 31st Millennium. The prison was located in Anatolia under the mountain peak of Rakaposhi, and was built at least a thousand years before by persons unknown. The prison was home to some of the worst criminals from the Imperium and tyrants from the Unification Wars, and some had cells designed for them by the Emperor himself to ensure they would never escape, there was even a cell constructed for Horus Lupercal.

The prison's cells and walls were cut from the limestone of the mountain and layered with adamantium plates, and cells used to house psykers had psi-resistant crystals built into the walls. There were multiple security systems in place to ensure that prisoners could not escape, including cell blocks that would drop into abysmal holes in the earth during an escape attempt and servitors armed with autocannons and assult cannons.

During the Horus Heresy many of the Custodes that were normally stationed at the Vault were sent to help with the war or guard the palace, leaving the prison undermanned, this would eventually lead to the members of the Outcast Dead escaping.