Brotherhood - Attis War The Brotherhood - Attis War was a military conflict between the Texas Brotherhood of Steel led by High Elder Rhombus and the super mutant Attis Army , starting in 2208 and ending in 2209 . 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 . They began to draw attention to themselves , and Rhombus , the 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 . However , Rhombus did not listen to the Elder council , and began 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 prototype Vault : 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 . Afterwards , 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 for 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 . 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 inside the Secret Vault . However his army remained blocked at this level as they could not gain access to the lower level , which required a key card . Triggering a siege on the city to get the key card and go to war with the Church of the Lost , Attis continued to prepare his plan . Later in 2209 , the Initiate ventured into Los , destroyed the weakened Church of the Lost , killed Blake ( the high priest of the cult ) and arrived at 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 soldiers of Attis ' army and entered the Hub chamber of the residence area . Refusing to give the Initiate the key card , Attis engaged the Initiate in combat , using his retractable arm blade to fight . When Attis lost , two nightkin appeared and quickly stunned and captured the Initiate . Taking the Initiate 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 the Initiate into the pit . A few moments later , the Initiate encountered Mary in the ruins , who assisted him in finding his way to the garden , where all survivors of the Vault 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 attacked Attis , he tested it on himself , and found that the FEV was unable to make mutants fertile . However , an unforeseen consequence followed , revealing another side - effect of the Vault - Tec modified FEV ; it led to strange side effects , and Attis ' 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 his 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 Brotherhood - Attis War occurs in " " .