Attis Army Attis Army is one of the two most important offshoots of the Master ' s Army , along with the Gammorin ' s Army , led by an old important commander of the Master ' s Army called Attis . Background . Attis was one of the commanders of the faction of super mutant s who fled to the East after the death of the Master and the destruction of Mariposa Military Base . Starting to talk about themselves , Rhombus , now High Elder of the Brotherhood of Steel , thinking they were a threat , demanded during the elder council that the Brotherhood look into it . But the elder council answered in the negative , because the former expedition grew by similar ambitions ( track down and assess the extent of the remaining super mutant threat ) against the Gammorin ' s Army , and the incident ensuing divided the Brotherhood , creating a splinter faction of the Brotherhood of Steel . But Rhombus didn ' t listen to the elder council and started a crusade against the Attis Army . With some Scribes and Paladins , he mounted a new expedition which was later named Texas Expedition and began tracking the Attis Army . They followed their trail to Texas and there , he discovered the Vault Prototype , an abandoned vault prototype dedicated to the Secret Vault project and installed the main base of the Brotherhood of Steel in Texas . The Attis Army searched for clues regarding the history of FEV before trying to make the Master ' s plan a reality , and learned about a secret Vault - Tec installation called the Secret Vault , the Vault - Tec private Vault after the Great War , with new and possibly improved versions of the FEV virus . During the travel , the army came across the Carbon Mill and encountered , the raider matron of the largest and powerful raider gang of Texas , who offered to sell slaves regularly . After that , the army traveled to the ghoul city of Los in Texas , where the Secret Vault was located . Their first goal was to rebuild the mutant army and develop a cure to mutant sterility . The Secret Vault gave Attis hope , as the Vault scientists ' research was dedicated to improving the original FEV in order to maintain reproductive functions . Arriving in Los , Attis attempted 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 Paladins . The Brotherhood of Steel group was annihilated and Rhombus was captured . Attis used this confusion to his advantage and managed to get into the Secret Vault . However his army remained blocked at this level because they couldn ' t gain access to the lower level , which required a key card . Triggering a siege on the city to get the key card and going to war with the Church of the Lost , Attis continued to prepare his plan . 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 area . 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 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 . Attis had penetrated deeper into the Vault , until the last section of the laboratory , and in the laboratory core he had found the Vault - Tec modified FEV . Just before the Initiate arrived and combat started , he tested it on himself , and found that this FEV is unable to make mutants fertile . However , an unforeseen consequences followed , revealing another potential of the Vault - Tec modified FEV ; it led to a strange side effects and his skin turned darker . During the battle , Attis exploded and decomposed into a strange organic biomass , a rapidly - multiplying multicellular organism that covered the entire laboratory section of the Secret Vault . In this gigantic form , Attis tried to make the rest of the Attis Army found in the Secret Vault " join " him , but they were scared of him and began to fight back . After the Initiate found the Vault ' s nuclear warhead , he triggered it and escaped with a monorail , destroying the Attis Army , Los and the Secret Vault . Appearances . The Attis Army appears only in " . "