Fallout: Ranking Every Vault From Least To Most Horrifying
4. Vault 75 - Refining Human Genetics/Parents Executed
Vault 75 appears in Fallout 4, and is located under the Malden Midden School.
In 2077, as the nuclear bombs began to fall, everyone who was meant to be in the Vault managed to make it in time. This included a lot of children from the school, as well as their parents and teachers.
What happened next is extremely dark. The security staff separated the children and the adults, then took the adults for 'orientation'. In reality, they were taken off and killed one by one, leaving behind the children.
The whole purpose of the Vault was to manipulate the gene pool of its residents, using the best and brightest to create stronger, more intelligent humans. The children left behind were then subjected to almost torturous levels of mental and physical testing, and conditioned to fear the surface, also known as 'Uptopland'.
When a resident turned 18, they 'graduated' from the Vault. This meant that for the most part, their good genes were harvested for further use and they were killed, while some were drafted into the Vault's science team.
Anyone else deemed not strong enough, intelligent enough or with enough 'good genes' was then executed upon their graduation ceremony too.