Fallout: Ranking Every Vault From Least To Most Horrifying
3. Vault 87 - FEV Virus Vault Where People Were Exposed To The Virus
What better place to conduct your morally-questionable experiments than underground in a Vault below Fallout 3's Capital Wasteland?
That's exactly what Dr. Wayne Merrick and his team did. The original purpose of Vault 87 was completely scrapped, and Merrick started experimenting with the Forced Evolutionary Virus to create humans able to survive the nuclear wasteland.
The poor humans in the Vault were 'dipped' in the FEV virus vats, where they remerged hideously disfigured, dead, or - ultimately - transformed into Super Mutants.
At some point, a nuclear explosion above the facility caused several test subjects to escape, where they promptly either killed or mutated the remaining human staff. Since that time, the Super Mutants reach the surface, where they routinely grab humans and return them to the Vault to mutate them into new Super Mutants.
Super Mutants are sterile you see, and the only way they see to make their species survive is by creating new ones.
By the time the Lone Wanderer comes around, the Super Mutants are running low on the FEV virus, and are scouring the Capital Wasteland to find even more.