The Most Horrifying Vault Experiments In The Fallout Franchise (So Far)

Without a doubt, one of the highlights to Prime Video's addition to the Fallout franchise with the first live-action series season for many people who watched it is watching Norm stealthily uncover the secrets behind the combined network of Vaults 31, 32, and 33 and Lucy discover the truth behind Vault 4's history. While these storylinees were a nice addition for even newcomers to the franchise, Vault experiments have always been part of the games, and have long been a favorite type of side quest for players to handle themselves to uncover Vault-Tec's secrets.

While undoubtedly the franchise has plenty more disturbing experiments planned to present to players and audiences of the series, particularly with live-action presenting more realistic versions of these horrors to viewers, there are already plenty of upsetting experiments to experience in the franchise's games. Below are twelve that deserve to be seen and are, in my opinion, the largest displays of Vault-Tecs cruelty.

Vault-Tec's Villainy in the Vaults

In no particular order and only utilizing vaults that have appeared canonically in the franchise so far, here's my personal list of favorites that really scratch the constant itch for more horror my brain has:

Vault 87

First Appearance: Fallout 3

The birthplace of the Capital Wasteland's super mutants and centaurs, Vault 87's original experiment was scrapped in favor of subjecting the humans inside to the Forced Evolutionary Virus (FEV). While initially after infection the side effects didn't seem to dire, with notable changes being asexuality, increased upper body strength in men and eventually thicker skin in both men and women, the project was ultimately a failure. The first subject to succumb to their effects was a women who'd lost so much of her brain function she could no longer live, and following her passing the other subjects had to be euthanized due to their increased rage.

Standard security measures for the vaults weren't enough to keep all of the test subjects inside, however, and some broke free only a year after the vault was sealed. Because of this, super mutants kidnap humans from all over the Wasteland and bring them back to the vault to be mutated, finding themselves having to spread their population in order to find a new source of FEV to infect more humans in the future as the vault's supply has been dwindled.

Vault 12

First Appearance: Fallout

Vault 12 is a particular breed of cruelty, providing the humans seeking refuge in it with an entirely false hope of protection. Described as being "built with every amenity in mind for the prospective Vault Dweller," ultimately Vault-Tec's true intentions with the residents here was to study the effects of radiation on the residents...which is exactly why the vault was built with a door designed not to close. After the populace of Bakersfield rushed to their shelter for safety, they all faced ghoulification when the door operated (or rather, didn't operate) as intended by Vault-Tec.

Vault 77

First Appearance: One Man, and a Crate of Puppets

Featured in a promotional comic strip released to promote Fallout 3, this is a personal favorite display of Vault-Tec's cruelty as it's one of their more intense psychological based experiments. Try to imagine a more horrific scenario than being the only person sealed inside of a vault, and if you can't, you'll probably already have some sense of empathy for this fictional character as that's exactly what happens to the individual who comes to be known as "Puppet Man." After being sealed in he begged for the "other fucking people" to be let in, pleas that would go unheard and result in his deteriorating mental state over years of solitude. Eventually, the unnamed man finds a crate of puppets that he begins to play with an ultimately begin to believe they're talking to him, his madness pushing him to rip apart one of the puppets and flee the vault out of fear for what the dog puppet would do to him.

The events at Vault 77 can likely be considered canon to the franchise considering you can find a Vault 77 suit and holotape next to it in Paradise Falls that mention him, stating that the jumpsuit "freaks the boys out" because of a story about a "stranger with no name," fearing that if the jumpsuit belongs to the man, he might come back for it some day.

Vault 75

First Appearance: Fallout 4

Located underneath a middle school, the vault was paraded as a safe place for children to flee if a nuclear bomb was dropped during school hours. When the bombs were dropped the students, their families, and the teachers were all able to successfully seek refuge in the school...though the children were immediately separated from the adults, who were executed under the guise they were being taken away for "orientation." The vault was created with the intention to last many generations and allow for the "refinement of human genetics" through selective breeding, genetic modification, hormone treatments, and the experimentation on and cultivation of embryos.

Vault 108

Vault 108 was designed to be doomed from the beginning – while Vault-Tec claimed the vault had enough supplies for 38 years, the reality is it was only equipped for 20 years of power. In addition to this, the vault was supplied with an overabundance of weaponry. As if this wasn't enough, scientists eventually began performing cloning experiments on the same man, Gary, repeatedly. These clones were all created with violent tendencies that led the vault to its doom.

Vault 112

Within Vault 112 is a sparse population of vault dwellers, all of whom are imprisoned in a simulation of pre-war America. Created by Dr. Stanislaus Braun, the director of the Societal Preservation Program, who installed a simulation in Vault 112 called Tranquility Lane. While on paper it was meant to allow the residents to live perfect lives virtually, away from the horrors of the real world, Dr. Braun used his administrative powers to terrorize the population. Taking on the avatar of a young girl, he'd virtually kill his residents, wipe their memory, and bring them back to life to do it all again. While he could permanently kill his residents, he could not die in the simulation.

Vault 19

First Appearance: Fallout: New Vegas

While there's plenty of potential for physical horror in a world of radioactive fallout and scientific experiments, that doesn't mean the distressing things inflicted onto the Vault's citizens stop at bodily horror. One of the most striking examples of psychological horror in the franchise is inflicted upon the residents of Vault 19. Taking the idea red vs. blue to a new extreme, residents were divided by red and blue, each side having their own overseer and contact between the two factions extremely limited. Being subjected to artificially induced paranoia, eventually the two sides began to blame each other for the misfortunes that were befalling them, though it's truly Vault-Tec and their overseers behind it all.

Vault 22

First Appearance: Fallout: New Vegas

The results of something that could've been purely good and provided sustainability to life in the post-nuclear fallout, the results of the experiment went awry due to specialized fungus that was used to keep pests from ruining crops. Unfortunately, the fungus had mutagenic properties, and the spores took root in human hosts, transforming them into spore carriers, deadly and incredibly aggressive cannibals.

Vault 106

Starting ten days after the vault door was sealed, psychoactive drugs were being pumped into the vault through the air filtration system. The overseer and the vault personnel had orders from Vault-Tec to lie to the residents who began to report symptoms. Eventually, the residents became delirious and violent, an ordered lockdown from the overseer not enough to stop the vault's security from being overrun. By 2277, the vault is in ruin and filled with insane survivors, the drugs still being pumped through through the air.

Vault 95

First Appearance: Fallout 4

Created as a rehabilitation center for people suffering from a chem addiction, Vault-Tec always intended to allow these residents all the drugs they could ever want after a five year period of sobriety. Immediately upon the stash of drugs being opened by the overseer, who had noted along the way the success of the program and that recovery from addiction was possible, the residents unfortunately mostly reverted. Some didn't take long to succumb to using again, violence broke out, and the familial bonds that had developed over time were long forgotten. Some were able to resist the urges, and others came to realize the situation was intentional and recorded their anger at their betrayal.

Vault 11

Honestly, Vault 11 is probably overall one of the worst things Vault-Tec did, which is saying a lot considering the things that have already been covered in this article. Nonetheless, Vault 11 more than earns its spot by having an AI in control that demands that vault's residents select one individual to be sacrificed, facing all of them being terminated if they don't, repeating this yearly until only five of the survivors are left.

With their population almost extinct, the AI informs the group of five that they will be allowed to leave if they refused to sacrifice anyone. Mentally wrecked from years of guilt and being responsible for the death of someone you've been in isolation with for years, four of the five decided instead to take their own lives.

The fate of the fifth survivor is one of the franchise's mysteries.

Vault 4

First Appearance: Fallout live-action series

Vault 4 is still fresh in the brain, and honestly the things the people in this vault were subjected to will definitely be sticking there for a while. The population here faced the consequences of experimentation performed by the original inhabitants of the vault, many people suspended in cryogenic stasis for centuries while women had pregnancy forced upon them with mutated experiments, often resulting in their deaths. The vault's victims are able to rebel and turn the vault into a haven for those who have faced Vault-Tecs cruelties.

I think the fact that Prime Video was willing to incorporate such a twisted storyline full of horrifying experiments shows they're willing to embrace the more bizarre, outright horrifying vault stories. 

Clearly, Fallout 3 and Fallout 4's lead writer Emil Pagliarulo set out with the intention to demonstrate the horrors of Vault-Tec in full, amplifying the experiments in these games into some of the franchise's more horrific examples of human depravity to land them more than half of the presence on this list. As for the future, Fallout 5 is likely still quite a ways away, and fans of the franchise also have season 2 of the Fallout series to look forward to as well, both of which will almost certainly provide future additions to this list.

Is there a particular vault experiment you particularly enjoyed uncovering, and is there one you'd like to see translated into live-action? Chat with me about the horrors of Fallout on X at @amazingspidrhan!