| ||For the quest, see Vault 81 (quest).|
Vault 81 is unlike almost any other known vault in the Commonwealth, in that it still contains sane and active dwellers. After a simple quest requiring either three fusion cores or a successful 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 propulsion nozzles.
The first vault overseer, Dr. Olivette, was skeptical of Vault-Tec's goal and 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, but Vault-Tec had major backers in the federal government. She realized blowing the whistle would do nothing. 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 with two living nearby, Kenneth Collins and Jim Flint, coming over with the general population, and the third one, Burrow, 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 Phase II, animal testing, and Phase III, human testing on unknowing participants.
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.
By 2287, one of Vault 81's dwellers, Bobby De Luca, 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 gaining 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.
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- Syringer rifle - Reward from the quest Hole in the Wall.
- Medicine bobblehead - In Curie's laboratory, during the quest Hole in the Wall.
- Mini nuke - In the broodmother's room, inside a tipped over locker, during the quest Hole in the Wall.
- Stealth Boy - In same room as the Vault 81 tech password, during the quest Hole in the Wall.
- Fusion core - Reward from the quest Here Kitty, Kitty, and one during the Hole in the Wall.
- Overseer's Guardian - For sale at Alexis Combes' shop. She also has Destroyer's right leg and overseer's armor.
- Taboo Tattoos issue #16 - In Horatio's barbershop.
- Grognak the Barbarian issue #5 - In the classroom, as a reward for the side quest Short Stories.
- 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.
- Vault 81 tech password - in the Secret Vault 81 research comm room, during Hole in the Wall. Gives access to nearby secure access terminal.
- Teddy bear - A unique clean variant can be found in a box before one of the beds in the northeast bedroom.
- If one is bitten by the mole rats in Vault 81, their maximum HP will be reduced by 10 points until the vaccine from the quest Hole in the Wall is used. This will however affect the outcome of said quest negatively.
- If one manages to escape without being bitten, the cure can safely be given to Austin and the quest is completed without suffering from the health penalty.
- The Hole in the Wall quest can be difficult to initiate, and requires 24 hours of sleep outside the vault to begin or to just complete the quest Here Kitty, Kitty.
- If one is still wearing the Vault 111 suit, the Vault 81 inhabitants will comment on their vault suit. Although sometimes they will comment on the player character being from a vault without them wearing the vault suit, or having interacted with them before.
- If one brings Codsworth, the Vault 81 inhabitants will compare it to their vault's Old Rusty.
- If one brings Dogmeat, Preston Garvey, MacCready, Cait, Paladin Danse, Hancock, Strong, Piper or Nick Valentine, the vault security will ask Overseer McNamara for permission to allow entrance.
- There is an audio file for if you have a second companion along with Dogmeat when first entering. This is only accessible either in the game files or through using mods such as "Everybody's Best Friend" that allow you to have an extra companion.
- If one brings Deacon, he will change his disguise into a Vault 81 jumpsuit.
- If one brings Paladin Danse, vault security will sarcastically question his seriousness.
- If one brings X6-88, some dwellers may recognize him as an Institute courser.
- If one brings Curie (after enabling her as a companion), she will request to leave the vault, even though she will still follow the player character.
- If one is wearing a suit of power armor, there will be numerous comments of both fear and admiration from the residents.
- If one is wearing a Silver Shroud costume, there will be comments about it being Halloween already.
- Following the successful completion of Hole in the Wall, the player character will be given a room by Gwen McNamara.
- In a strange twist of fortunate irony, the original overseer's change of heart led to the vault serving in its advertised role: 'a shelter for its residents in the event of a nuclear attack'.
- In the reactor area, five wooden blocks can be found on top of two machines, spelling out 'BS' and 'LOL.'
- Fusion cores handed in can be anything from 1/100 to 100/100.
- When first entering the vault, the Sole Survivor will be asked to go see Dr. Forsythe. He will then ask for a donation of blood for his research, to study the change in the human DNA.
- In a random encounter, the location of Vault 81 can be marked on the map by speaking to Rylee, a Vault 81 resident who left to wander the Commonwealth.
- In another random encounter, the player character can come across a band of raiders holding a Vault 81 resident hostage. Upon killing the raiders, should he survive he will thank the player character and return to the vault.
- It is also possible to get Vault 81 marked on the map by picking up Dr. Forsythe's note, if found in the Commonwealth.
- All the clocks in the vault are stuck at 9:47, meaning the residents have made no effort to repair them, even after 210 years.
- After completing the Brotherhood of Steel ending, a Brotherhood of Steel knight may be eternally standing guard outside the cave leading to the vault door.
- After gaining access to Vault 81, the vault control panel will be considered an NPC saying normal lines like: "Yeah?" or "Huh?"
- Caravans can sometimes be found outside the vault entrance as it is one of the stops on their route.
- The kids in the classroom may be seen taking the G.O.A.T. but this happens rarely.
- During the pre-War beginning of the game, the news anchor on the TV notes that there are still openings in Vault 81.
Vault 81 appears only in Fallout 4.
- pc xboxone ps4 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 through the "KillAll" 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. Note: On Xbox One, fast traveling from and returning to the vault resolved the issue. You can also destroy these turrets in VATS using critical hits. [verified]
- xboxone ps4 After using the speech check, the main door never opens. Reloading to an earlier save (before the speech check) can fix this.[verified]
- ps4 pc xboxone The vault security guards will sometimes refer to the male Sole Survivor as a female. [verified]
- xboxone 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 third person.[verification overdue]
- pc Holt Combs will disappear after exiting the vault occasionally this can be fixed by using the elevator and searching again. [verification overdue]
- pc ps4 xboxone Dr. Penske will give a quest to deliver fertilizer for 25 caps a piece however after agreeing she will give standard dialog when prompted to talk. [verified]
- pc Quest will randomly complete, without actually starting quest. The quest then disappears from Pip-Boy.[verification overdue]
- After doing the Hole in the Wall quest, Alexis and Holt Combes will be dead in their room.[platforms tag needed][verification overdue]
- pc 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)[verification overdue]
- xboxone When you enter the room next to the surgery, there is a green stool between two beds, sitting on it and dismounting gives you the ability to walk through the wall behind you, once between the generator room and the bedroom, you can walk up and down the gaps, if you go straight through to the generator room, you will get stuck behind the small cabin where the computer is and a crate. Another option is to move between the walls towards the surgery back room, entering there leaves you trapped behind the shelves and the chair (you cannot sit on the chair to escape); both of those options won't give you the option to escape, the third area is an empty room with no flooring, if you walk towards it, you fall down where you end up on the next floor up where you don't need to restart the game. [When you're between the rooms, you can see through to the end of the whole vault, but it's all unrendered and you can see that the foundation of the whole build is built on flat earth (mud), interesting note to point out is that when you look at the distance, whichever character (or weapon), loading animation shows when the game loads the area that you are in, the loading character (or weapon)shows up as the backdrop image, but it's shown as just a still image, not like the revolving animation.. which shows the mechanics of the whole game]
- ps4 xboxone When the Overseer takes over Vault Security in asking questions about you, using Charisma to get yourself into the vault will cause a glitch where you cannot enter the door to the elevator, leading to lower levels of Vault 81 (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 playes must accept the overseer's exchange by delivering three Fusion cores instead of using Charisma.[verification overdue]
- ps4 pc 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.[verification overdue]
- xboxone Part of the wall at the end of the hallway opposite the classroom doesn't load and is a blank space. [verification overdue]
- pc xboxone 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 prid 00153855 then moveto player OR by turning clipping off with tcl and walking through the wall and opening the hidden door. Immediately after opening the door, reopen console and turn clipping back on so you can actually enter as it won't let you change cells with clipping off. Once in the room, open console and select Calvin or any other "stuck" NPC and click on them so their ref. ID is on-screen. Close console and exit via the door. It will exit you directly in front of the bathroom door. Now reopen console and type moveto player. To prevent NPC from returning to the holding cell, go back into the wall, select the door, then type lock 1. Move POV so the the "Unlocked" message disappears, then look at door again, it should now say "Novice Lock". NPC will not be able to unlock this and will stay in the halls if they don't have an assigned room. May need to run to other end of hall and use the moveto player command there, then run back to get the other as they'll make a bee-line right back. Other option is to write all ref. ID down and use the prid command. [verification overdue]
- pc ps4 During the Hole in the Wall quest, at the first patch of dirt where the mole rats spawn, there are some stairs, sneaking whilst climbing the stairs may cause you the get the mole rat disease without getting bitten. [verification overdue]