Attis

Attis is a highly intelligent super mutant and was an important commander in the Unity. After the destruction of the Master and the vats nearly five decades ago, he created the "Attis army" from remnants of the Master's army. He then began searching for clues regarding the history of FEV before trying to make the Master's plan a reality. Attis believes mutants deserve to inherit the planet after humanity annihilated much of it during the Great War.

He has a vindictive attitude towards the Brotherhood of Steel and around 2208, he became their greatest enemy. He is the main antagonist and the final boss of Fallout: Brotherhood of Steel.

Background
Attis is one of the few super mutants with great strength both intellectual and physical, like the Lieutenant or Marcus. He is tall, strong and quite athletic for a super mutant. He is also very fast and knows how to use all kinds of weapons. After the death of the Master and the destruction of the vats, he created and became the general of the faction which tried to continue the Master's work; rebuild the army and transform the entire human race into super mutants, to have a single race able to survive - thrive in the wasteland, eliminating any differences and removing all discord.

After Attis created his own army, he took his group into hiding, searching for clues regarding the history of the FEV. Throughout the years, he and his army led a guerrilla war against the Brotherhood of Steel, (still looking for the rest of the mutant army because of the failure of the Airship's expedition that created the Brotherhood of Steel), eventually forcing Rhombus to start a crusade named "Texas Expedition" in order to annihilate the remaining super mutant threat.

Attis learned about a secret Vault-Tec installation called the Vault-Tec Corporate Vault after the Great War, with new and possibly improved versions of the FEV. He led his group to the ghoul city of Los in Texas, where the vault was located. His first goal was to rebuild the mutant army and develop a cure for mutant sterility, as the vault scientists' research was dedicated to improving the original FEV in order to maintain reproductive functions.

Arriving in Los, he tried to negotiate with the Church of the Lost, the cult that controlled 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 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 Vault-Tec Corporate Vault. But to access the laboratory section, he had to get a key card, only possessed by the Church of the Lost.

Besieging the city to get the key card and going to war with the Church of the Lost. He continued to develop his plan and allied himself with Jane, the raider matron from the largest and most powerful raider gang in Texas located in Carbon. She sold him human slaves from raids in Carbon, and he goes into Carbon himself to retrieve them personally. They now became slaves of Attis but their function in his army remains unknown. Attis then leaves Jane after concluding his business with her, while mentioning he thinks she's repulsive and selling her own kind.

Continuing his plans for the war against the Church of the Lost and to get the key card, the Initiate changed the deal, destroyed a weakened Church of the Lost, killed Blake, the high priest of the cult and came to the Vault-Tec Corporate Vault to destroy both Attis' army and the vault itself with the key card stolen and hidden by Rhombus, preventing Attis from exhausting his army in a long drawn-out siege. Refusing to give him the key card, Attis engaged in combat, using his retractable arm blade to fight. Though he loses, two nightkin appear and quickly stun and capture the Initiate, taking them to an area with a huge pit down in the Vault-Tec Corporate Vault Ruins. Attis took the key card, cut off the Initiate's arm and commanded the nightkin to throw them into the pit. However, thanks to Mary, the Initiate managed to survive and later even received a new arm through a regeneration experiment.

Attis penetrates deeper into the Vault, until the last section of the laboratory, the laboratory core and found the Vault-Tec modified FEV. Just before the Initiate arrived and combat started, he tested it on himself. It was revealed that this FEV is unable to make mutants fertile. However, an unforeseen consequence followed, revealing another potential of the Vault-Tec modified FEV, it led to a strange side effect and his skin turned darker. During the battle, he mutated again, growing and reaching the size of a super mutant behemoth and all his injuries were healed. After being seriously injured again by the Initiate, the modified FEV proved highly unstable, causing Attis to regenerate uncontrollably due to the amount of damage he received. He exploded and coalesced into a strange biomass, a rapidly-multiplying multicellular organism that covered the entire laboratory section of the Vault-Tec Corporate Vault. Though initially he believed his discovery lead to nothing, soon he began to realize the new potential of the virus.

This new creature began to grow with each second, and its various organs, eyes, mouths and tentacles began to grow out of the floor. This organic nightmare retained some of Attis' consciousness, starting to dream of a new world, similar to the Master's Unity. In this gigantic form, Attis tried to make the remaining super mutants in the vault "join" him, but they were scared of him and fought back. The Initiate ran from him, fighting his tentacles, his giant "heads" with one eye and several fleshy walls with big mouths in the center of them. Eventually, they found Patty, the vault security officer, now enveloped in a cocoon-like state by Attis, being slowly digested. She revealed that there was a way to start a self-destruct sequence, and asked the Initiate to kill her. In the next room, the needed terminal was found, and the Initiate escaped using the vault's monorail, while the vault's nuclear warhead, specially designed for this purpose, detonated, killing Attis.

Appearances
Attis appears only in Fallout: Brotherhood of Steel.