Khangba Marwu, also known as The Vault, was a large underground Imperial prison complex on Terra intended to hold the worst criminals of the Imperium of Man. Its inmates were overseen by the Legio Custodes during the 31st Millennium. The prison was located in the Himalayan Mountains under the mountain peak of Rakaposhi, and had been constructed at least a thousand standard years before the Horus Heresy began by persons unknown. The prison was home to some of the worst criminals of the Imperium and had been used to imprison several of the tyrants defeated by the Emperor's forces during the Unification Wars. Some of these warlords, such as Uilleam the Red, the Prince of Albyon, the Ethnarch of the Caucasus Wastes and Narthan Dume, the Tyrant of the Pan-Pacific Empire, had cells designed for them by the Emperor Himself to ensure that they would never escape. Dume himself was executed at the urging of Contantine Valdor, the Captain-General of the Legio Custodes, soon after his capture, but many of his lieutenants eventually found themselves incarcerated within The Vault. Once the Horus Heresy began, a cell that was never occupied was also prepared for the traitorous Warmaster Horus. The prison also became a dumping ground for the Outcast Dead, those members of the Traitor Legions who had been stationed on Terra as part of the Crusader Host, an Astartes honour guard that had once served in the Imperial City on the outskirts of the Imperial Palace.
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 abyssal holes in the ground during an escape attempt and Combat Servitors armed with Autocannons and Assault Cannons.
During the Horus Heresy many of the Custodes that were normally stationed at The Vault were sent to reinforce Imperial units fighting the Traitor Legions or increase the Imperial Palace's security, leaving the prison undermanned, and this weakened security would eventually allow the members of the Outcast Dead to escape from The Vault.
- Custodian Uttam Udar - Head Gaoler
- Custodian Sumat Tirtha
- Natraj - Soldier of the Uralian Stormlords
- The warlords of the Pan Pacific Tyrant, Narthan Dume
- The Ethnarch of the Caucasus Waste
- The Reaper
- Uilleam the Red
- Prince of Albyon
- Warlord Kibuka
- Zamora - Supposedly an officer in the Emperor's pre-Legio Custodes bodyguard
- Adept Exemptus Atharva of the Thousand Sons
- Sergeant Tagore of the World Eaters
- Marine Subha of the World Eaters
- Marine Asubha of the World Eaters
- Marine Severian of the Luna Wolves
- Marine Argentus Kiron of the Emperor's Children
- Marine Gythua of an unknown Space Marine Legion
- Astropath Kai Zulane
- The Outcast Dead (Novel) by Graham McNeill