Vault 81

Vault 81 is a fallout shelter developed by Vault-Tec, located in the Commonwealth in 2287.

Background
Vault 81 is unlike almost any other known vault in the Commonwealth, in that it still contains sane and active dwellers. The old overseer's terminal (which is stored in the generator room) makes a heavy implication that this success is not due to them having a more benign experiment to conduct (like with Vault 101), or simply being a control vault with no experiment (like with Vault 76), but rather because the original overseer actively sabotaged Vault-Tec's original mandate by refusing to carry out the initial experiments.

After a simple quest requiring either three fusion cores or completing a difficult speech check, the Sole Survivor can gain entrance and meet the vault dwellers.

Vault-Tec created Vault 81 with the purpose of developing a single, universal cure for every sickness that humanity could possibly suffer from, using the residents as human test subjects. The vault was divided into two separate areas; the main vault, where up to 96 residents would make their home for the foreseeable future and the secret vault, where Vault-Tec scientists would conduct their research and observe the residents as they were unknowingly exposed to different diseases and cures. The diseases were released via propellant nozzles hidden within the resident's rooms. In the case of an evacuation of the vault, all main vault residents were to be incinerated with the same propellant nozzles.

The first vault overseer, Dr. Olivette was skeptical of Vault-Tec's goal and the possible use of human experimentation. She planned to blow the whistle if it was found to be unethical. However, when she received her full briefing she found out the true nature of the experiment she also discovered that Vault-Tec had major backers in the federal government, rendering blowing the whistle as moot. Dr. Olivette was determined to not let the residents of the vault be used as guinea pigs and tried to think of a plan. On the morning of the Great War, Dr. Olivette received the "call" to start the notification of staff and residents but sabotaged the call list so the science staff wouldn't be notified and report in. Her plan mostly worked; however, three of the science staff turned up. Kenneth Collins and Jim Flint came over with the general population and the third one Burrow was visiting to ask when the next drill would be. As the three scientists worked to create their cure, Olivette watched over all of their data and personally had to approve the scientists moving onto Phases II and III, animal testing and human testing on unknowing participants respectively.

Before human testings could begin, Olivette disabled the delivery systems, cutting off the scientists from infecting the vault dwellers. Additionally, she also sealed all access points to the secret vault, leaving the three scientists to die. To prevent any commotion within the general population, Olivette kept the vault's true purpose and the existence of the secret vault a closely guarded secret.

Isolated from the other side of the vault the scientists continued to use animal testing with their last remaining population of mole rats. To help with the research, Dr. Collins modified a Miss Nanny lab assistant to take on greater responsibilities due to the staff shortage, creating Curie. When the scientists eventually died of old age, Curie remained and worked on the cure alone, spending decades conducting trial after trial. She achieved the vault's objective in 2204, perfecting the universal cure. Although Curie had reached a level of self-awareness over the years she was unable to overcome her original programming, which required authorization from a Vault-Tec employee in order for her to leave the vault and begin a new line of research. She patiently idled in the secret vault for decades, awaiting a response from vault security.

Meanwhile, the residents in the main vault went on with their lives completely unaware that anything was amiss, or that they had been intended as test subjects. In 2277 Overseer Baht opened the vault for the first time, allowing communication and trade with the outside world. Although this provided a badly needed source of food and other vital supplies, especially parts and tools to repair the vault's deteriorating systems many residents maintained an isolationist or even xenophobic mindset, distrusting any outsider who was allowed to enter.

In 2287 Bobby De Luca, one of Vault 81's dwellers had discovered one of the entrances into the secret vault and used it to store his drugs. Austin Engill witnessed Bobby opening the door and went in to investigate. He was bitten by one of the lab mole rats, which had escaped containment and started a colony in the secret vault decades before. This nest was still infected with the various diseases used in the experiment, resulting in Austin acquiring an unknown lethal disease. When Bobby revealed the existence of the secret vault, the Sole Survivor agreed to search it for a potential cure. Inside, the Sole Survivor discovered Curie who handed over the last unexpired dose of her universal cure. The Sole Survivor could either use it on themself, leaving Austin to perish and earning the animosity of the vault dwellers or turn it over to save Austin and be granted a room in the vault by Overseer McNamara and appreciation throughout the vault.

Layout
Vault 81 is divided into two main areas: the regular vault, where the residents live, and the secret observation area, where the scientific team used to observe the vault dwellers and conduct research. By 2287, the secret area is overrun by a special breed of mole rats while the regular vault is still functional and inhabited by vault dwellers.

There are two entrances from the main vault to the secret vault: an elevator located in the lobby, and a secret door in the reactor room. Although the elevator cannot be used until the end of the quest Hole in the Wall and the secret door is not unlocked before the beginning of the same quest.

Vault 81

 * Grognak the Barbarian issue #5 - In the classroom, as a reward for the side quest Short Stories.
 * Taboo Tattoos issue #16 - In Horatio's barbershop.
 * Overseer's Guardian - Sold by Alexis Combes. She also has Destroyer's right leg and overseer's armor.
 * Overseer's room key - On Jacob Forsythe and Gwen McNamara, opens sliding door in the overseer's room.
 * Vault 81 security key - On Scott Edwards and the vault security personnel. Gives access to various doors in Vault 81.
 * Technician's note - Next to the old overseer's terminal in a small room underneath the stairs in the basement where Bobby De Luca and Old Rusty work.
 * Syringer rifle - Reward from the quest Hole in the Wall.
 * Teddy bear - A unique clean variant can be found in a box before one of the beds in the northeast bedroom.
 * Six undamaged American flags can be found throughout the vault.
 * A complete Giddyup Buttercup can be found in the room diagonally across from Bobby De Luca's room, to the right of the restroom.

Secret Vault 81

 * Mini nuke - In the broodmother's room, inside a tipped over locker.
 * Vault 81 tech password - In the research comm room. The password gives access to nearby secure access terminal.
 * Stealth Boy - In same room as above.
 * Medicine bobblehead - In Curie's laboratory.
 * Vault 81 cure - Given by Curie.

Appearances
Vault 81 appears only in Fallout 4.

Bugs

 * When first entering the vault, you may be unable to open the door as the "You cannot do this while in combat" message will appear. This is because the two turrets on the ends of the wall are hostile, although they do not attack. The only way to "see" the hostile turrets is using VATS since they will also not appear marked on your compass. The turrets are also immortal, which makes all efforts of destroying them to continue futile.
 * The only known way to destroy them is via the console command, but this will also kill most residents and characters inside. The only known way of resolving this is opening the door while sneaking (completely hidden, a Stealth Boy is recommended). After, the animation will commence and everything will return to normal, but the turrets will remain hostile and immortal forever.
 * Another fix may be to fast travel from and return to the vault.
 * Another fix may be to sneak under the left facing turret until you are Hidden.
 * You can also destroy these turrets in VATS using critical hits or using explosions.
 * After using the speech check, the main door never opens. Reloading to an earlier save (before the speech check) can fix this.
 * The vault security guards will sometimes refer to the male Sole Survivor as a female.
 * On the surface, the button in the main elevator will be on the eastern side. While the elevator is in motion, the button will be on the northern side. When inside the vault, the button will be on the western side. This is most noticeable if the elevator is activated in the third person.
 * Holt Combes will disappear after exiting the vault. Occasionally this can be fixed by using the elevator and searching again.
 * Dr. Penske will give a quest to deliver fertilizer for 25 caps apiece however after agreeing she will give standard dialogue when prompted to talk.
 * After finishing the quest Hole in the Wall, Vault Security will refer to you as a woman even if you are a male character saying: "You're a brave woman. I wish we could've handled it ourselves, but no doubt, we'd have gotten eaten alive down here." (see gallery)
 * After entering Vault 81, the main elevator you see when you first come in may be non-existent, resulting in an Endless fall under the map which can easily be escaped by moving forward back onto the floor (Though any companions that happened to follow you will be endlessly falling). Reloading a save, or exiting and entering the vault again should fix it.
 * If access is gained to the vault via Charisma, a glitch will occur where you cannot enter the door to the elevator. Calvin and the Overseer will also be unable to open the door. The door or the button to the left of it would show "INACCESSIBLE". To access the door, the player must accept the overseer's exchange by delivering three fusion cores instead of using Charisma.
 * When in the secret Vault 81 the mole rats that come up from the ground freeze in some areas. It also causes them to sprout from the metal roofing of the facility.
 * Part of the wall at the end of the hallway opposite the classroom doesn't load and is a blank space.
 * After the first interaction with him, Calvin (the man who bought tools), will disappear and end up in the hidden "Vault 81 Holding Cell," which is a door hidden behind the residential area upper hallway wall, between the bathroom on the left of Holt and Alexis' room, and the wall immediately to the left of the security guard in the corridor at the top of the steps leading to the 2nd floor.
 * This can be temporarily resolved by opening console and typing then.
 * If the holding cell door was opened, go back into the wall, select the door, then type lock 1. Change the point of view so the "Unlocked" message disappears, then look at the door again, it should now say "Novice Lock". NPC's will not be able to unlock this and will stay in the halls if they don't have an assigned room.
 * There is an invisible footlocker underneath the bunk bed in the same room as the Giddyup Buttercup.
 * If the player character kills all of the Vault 81 dwellers, leaving only the essential NPCs and all children in the vault alive, and hasn't finished the tour that Austin Engill gave, once the player character exits the vault and returns back, all NPCs in the vault will return back to neutral. When the player character talks to Austin and decides to stop the tour, the player character will complete the quest and receive EXP despite not finishing the tour and killing almost all the vault residents. Some quests might be still able to start after this happens.