Vault-Tec Corporate Vault

The Secret Vault is the Vault-Tec's private vault, designed as an underground research facility where its high-ranking personnel after Great War can making their personal scientific research to survive the apocalypse and later enter the world having all the useful technologies and materials possible, behind the back of Enclave and the Vault Experiment. It was located under the city of Los Ybanez in Texas, know as Los after the Great War. The vault serves as a major research and production facility and, among its many technological artifacts, housed a special version of Forced Evolutionary Virus.

History
Like many major military contractors, as Vault-Tec grew in finances and responsibility, it began to develop highly experimental and secure technologies. In time, Vault-Tec was so thoroughly integrated with top-secret military research, it was practically a division of the U.S. government. The company still retained some elements of privatisation. So the principals of Vault-Tec - executives, scientists, and so on - had to be aware of the true function of the Vaults, and they had access to the technology. They were the developers. Regardless of the U.S. government's directives, Vault-Tec was not going to submit to a lottery and live underground with a bunch of human cattle in facilities that were intentionally defective. Thus Vault-Tec created their own facility, removed from the larger Vault network - and kept secret from the U.S. government. This facility is now known as the Secret Vault.

Vault-Tec didn't stop there. This secret, private installation was used to research the latest technologies that would benefit mankind in a post-nuclear environment. This included some extensive research with a "forced evolution virus" (FEV) which, unlike the government-controlled research at Vault 87, was kept secret from the government. It is known that the FEV in Secret Vault was highly modified to achieve its original goals, and avoid sterility (though unsuccessfully).

Other Vault-Tec projects that they intended to use for themselves were their own robotic systems, electrical weapons, special biological weapons program (the results are probably the unique radbugs and a variation of deathclaws), medical researches on restoring organic tissues damaged or mutated due to radiation, and their own tesla and power armor model.

The robots were implemented successfully and a special AI called CALIX was developed to control the Vault's systems. The tesla armor and power Armor project resulted in creation of one tesla version and two power armor version several though they were far less protective than T-51b power armor or Enclave's variants. The scientists experimented with animals and humans, and probably had a prototype of the government's biological weapon - the deathclaws, which were affected by their FEV research and heavily mutated.

The inhabitants of the Secret Vault not only lived in safety, but also attempted to study the new world above. There is evidence that they at least captured some brahmins and used them for both food and experimentation. Some time after the Great War, the Secret Vault was torn apart by a local civil war between Vault-Tec scientists and Blake, the chief security officer, who believed the researches with FEV and radiation, conducted on living subjects, including humans, were "evil". Their battles led to a major explosion that devastated the biological center section and enabled some species of radroaches and deathclaws, native to the Secret Vault, escape into the wasteland, at the same time allowing radscorpions and rats to invade the vault. CALIX also suffered a malfunction, and lost control over majority of the security robots. The people of the vault were divided. While many of them now reside in the garden, other separated groups could be found all around the vault, including the main residence level, where the majority of people still lived. However, many died due to monster attacks.

After the defeat of the Master, part of his army remained together, one part under the command of a former Master's commander named Attis. Highly intelligent and vindictive towards the Brotherhood of Steel, Attis took his group into hiding, searching for clues regarding the history of FEV. Learning about a secret Vault-Tec installation with new and possibly improved versions of FEV, Attis led his group to the area where the rumors started, the ghoul city of Los.

In 2208, arriving in Los, he tried to negotiate with the Church of the Lost, the cult that controls the city, but in vain. Just some time later, a contingent of Paladins of the Brotherhood of Steel lead by Rhombus arrived and a battle broke out between the Attis Army, the Church of the Lost and the Brotherhood of Steel paladins lead by Rhombus. The Attis Army used this confusion to his advantage and managed to get into the Secret Vault, killing the vault dwellers who were in the residence area, but his army remained blocked at this level because they can't access to other lower level, requiring a key card. Later In 2209, the Initiate come into Los, destroyed a weakened Church of the Lost, kill Blake the high priest of the cult and comes to the Secret Vault to destroy both the Attis army and the Secret Vault with the key card stolen and hidden by Rhombus. The Initiate killed many super mutants of his army and come into the Hub chamber of the residence part, where Attis resided, waiting for the Initiate to come.

Refusing to give him the key card, Attis engaged the combat, using his retractable arm blade to fight. Though he loses, two nightkins appear and quickly stuns and capture the Initiate. Taking him to an area with a huge pit down to the ruins, Attis took the key card, cuts off his arm and commands the two nightkins to throw him into the pit. A few moment after, the Initiate encounter Mary in the ruins, helping and leading them to the garden, where now all survivors of the vault are, giving them a new arm through a restoring organic table.

Later, after multiple chain of events, the Secret Vault was destroyed when the nuclear warhead was activated by the Initiate. With the vault, all of its researches and all of the experimental deathclaws, radroaches, super mutants, robots, and the heavily mutated Attis were destroyed. Only a few number of Secret Vault dwellers managed to survive using the auxiliary vent shaft to escape, turn off by the Initiate. The Initiate themself used the special monorail located in the lab to evacuate quickly to the secret exit in the mountains.

Layout
The Secret Vault consisted of five main parts: the laboratories, the facilities, the residence area, the garden and the biological center, who is now to a state of ruin. A nuclear device is located in the main frame section of the facilities part, in order to destroy the vault as an emergency decontamination procedures if the Secret Vault started to become too dangerous. A special monorail located in the first complex of the laboratories section should be used to evacuate the vault dwellers quickly to a secret exit in the mountains.

Inhabitants

 * Blake (leave)
 * CALIX (controlling Shop-Tec)
 * Ching Tsun
 * Dubois
 * Giese (leave)
 * Mary
 * Patty
 * The Technician
 * Secret Vault dwellers

Appearances
The Secret Vault appears only in Fallout: Brotherhood of Steel.

Behind the scenes

 * The Secret Vault is one of two known facilities to have done research on electrical weapons. The other was the Big Empty, a high-tech military research facility.