Fallout: Ranking Every Vault From Least To Most Horrifying
7. Vault 19 - Red Vs Blue
This New Vegas Vault was all about paranoia.
Upon entering the Vault, dwellers were assigned a side: Red or Blue. There were two distinct parts of the Vault governed over by two different overseers, and Vault-Tech did everything in their power to sow mistrust between the two different groups.
It's widely believed that this was done through subtle means such as subliminal messaging, high noises, weird drafts from vents and seeing blinking light patterns. The two sides blamed the other for this, but in reality, the two overseers, acting for Vault-Tech, were experimenting on both sides to study how paranoia is caused by extreme circumstances.
By the time The Courier, our protagonist from New Vegas shows up, the Vault is completely abandoned. The actual fate of its citizens has never been fully told.