Secret Vault The Secret Vault is one of the vault series of fallout shelters developed by Vault - Tec in northwest Texas underneath the city of Los Ybanez , known as Los after the Great War . This vault is located northwest of Carbon . History . Purpose . The Secret Vault is Vault - Tec ' s private vault , designed as an underground research facility where its high - ranking personnel could survive the Great War and continue to develop scientific , biological and technological advances , behind the back of the Enclave and the vault experiment . The vault serves as a major research and production facility and among its many technological artifacts housed a special version of Forced Evolutionary Virus . 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 . Research . 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 radbug s and a variation of deathclaw s ) , medical research 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 . Early years . 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 brahmin 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 , the chief security officer , who believed the research with FEV and radiation , conducted on living subjects , including humans , was " 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 . Attis Army . 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 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 couldn ' t gain access to other lower level , which required a key card . Later In 2209 , the Initiate came into Los , destroyed a weakened Church of the Lost , killed Blake ( the high priest of the cult ) and came 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 Attis ' army and entered 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 Initiate in combat , using his retractable arm blade to fight . When he lost , two nightkin s appeared and quickly stunned and captured the Initiate . Taking him to an area with a huge pit down to the ruins , Attis took the key card , cut off the Initiate ' s arm and commanded the two nightkin to throw him into the pit . A few moments later , the Initiate encountered Mary in the ruins , who helped and lead them to the garden , where all survivors of the vault now lived . When they arrived , the survivors gave the Initiate a new arm with a restoring organic table . Later , after multiple chains of events , the Secret Vault was destroyed when the nuclear warhead was activated by the Initiate . With the vault , all of its research and all of the experimental deathclaws , radroaches , super mutants , robots , and the heavily mutated Attis were destroyed . Only a small number of the Secret Vault dwellers managed to survive using the auxiliary vent shaft to escape , which was turned off by the Initiate . The Initiate used the special 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 , which is now in 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 . Notes . The Secret Vault is one of two known facilities to have done research on electrical weapons . The other was Big MT , a high - tech military research facility . Appearances . The Secret Vault appears only in " " .