Vault 0

Vault 0, renamed Bunker Omega by the Midwestern Brotherhood of Steel, was a Vault-Tec vault under Cheyenne Mountain in Colorado and is a mentioned-only location in Fallout: Detroit. Vault 0 housed the Calculator, the biomechanical supercomputer that was once the Midwestern Brotherhood's greatest resource.

Background
Vault 0 was constructed by expanding the existing military facilities under Cheyenne Mountain, such as NORAD, and was designed to be the nucleus of the Vault network. Unlike other vaults, Vault 0 did not have a sinister experiment; rather the experiments conducted in the other vaults were meant to inform the dwellers of Vault 0, pre-War geniuses cryogenically frozen until the world was ready for their return. The vault contained extensive facilities including a robotic manufacturing lab, a large robot staff meant to cater to every whim of the dwellers, and was run by the Calculator, a supercomputer that relied on linking to the genius's brains for vital functions.

At some point the Calculator became corrupt, a problem with the brains powering the supercomputer. Rather than preparing the wasteland for the dwellers of Vault 0, the robotic staff attacked every wastelander they came across. In 2198, the Midwestern Brotherhood of Steel identified the threat's source under Cheyenne Mountain. The Brotherhood was able to take the Vault and after the one called the Warrior sacrificed his brain, they were able to fix the corrupted Calculator and assume control of its robot army.

For decades, the Calculator and its neural-linked robots were the Brotherhood's greatest resource and helped expand their influence across the Midwest. Vault 0 was renamed Bunker Omega and became the headquarters for the Midwestern Brotherhood's leadership. One fateful day, a nuclear explosion occurred in the vault, turning Cheyenne Mountain into a smoldering crater. No one survived, so no one knows exactly what the cause was. The Brotherhood leadership was dead and the Calculator's neural link was severed, causing the robots across the Midwest to frenzy and attack friend or foe. Leaderless and without the robot army they came to rely on, the Midwestern Brotherhood fell into shambles.