The Vault is believed to be a cache of alien technology hidden on the planet of Pandora. Once rumours of its existence began to spread, the interest in its contents drew the attention of many, from small groups and individual prospectors to large-scale weapons manufacturers. The original intent of the corporations was to utilize the Vault technology for power and gain. A few select Vault Hunters are contacted by a Guardian Angel who reinforces belief in the Vault, and guides them on their mission to find it.
Borderlands 2 goes on to reveal that there is more than one Vault upon Pandora, as well as several other Vaults across the galaxy. Another Vault on Pandora, known as the Vault of the Warrior, houses an Eridian superweapon.
The Vault is an enigmatic place that is drenched in myth and folklore. After the Atlas corporation found a cache of alien weaponry on Promethea, legends began to emerge about vaults on other worlds. Popular myths and legends held that the Vault must contain something amazing. According to Marcus, the Pandoran Vault would give the finder advanced alien technology, fame, power, and women.
These legends, combined with the Atlas discovery, led to a "Gold Rush" of people heading to Pandora to settle in and look for the Vault. Even as the search continued and eventually waned, seasonal change on Pandora brought Summer upon the human inhabitants, and with it a new threat as the indigenous life awoke from hibernation and began to feed. Those who had once sought the legendary riches of the Vault found themselves under attack and with little to no further evidence of the Vault's existence they began to flee the planet. Those who could not afford to leave stayed behind, but the legends of the Vault remained.
Finding the Key
An archaeologist named Patricia Tannis, funded by the Dahl Corporation, was sent with a team to Pandora several years before the game begins to research the Vault and find out if it existed, where it was, what was in it, and how to open it. Tannis gradually lost her sanity thanks to the rigours of life on Pandora, while also becoming completely obsessed with finding the Vault as her team were systematically killed by the local fauna.
Through her research, Tannis discovered that the Vault could be opened at a specific date that came every two hundred years by using a special key comprised of three puzzle-like fragments. She recovered one of the Vault Key fragments, but ultimately lost it to bandits through a misjudged attempt to hide it. It was then that she realized she had a form of psychosis preventing her from leaving her camp at the archaeological site, so she remained there and sent out a call for Vault hunters to help her retrieve the key pieces and open the Vault.
Once the location of the Vault is uncovered and the key is assembled, the Atlas corporation uses its private military, the Crimson Lance, to seize the key and declare all contents of the Vault to be the property of Atlas. The Lance leader, Commandant Steele takes the key down the Descent, battling Guardians the whole way, and eventually opens the Vault.
Inside the Vault
When the Vault is finally opened, the truth of its existence is fully revealed. It was not the technology cache that the legends had spoken of, but a prison containing The Destroyer, an ancient and powerful monstrosity intent on consuming everyone in its path. Commandant Steele finds out too late the extent of her mistake as she and her men are brutally slaughtered in short order.
In the Borderlands official guide, it is revealed that the Eridians sacrificed their entire civilization to imprison the Destroyer inside the Vault. The Guardians were created to protect the Vault and prevent anyone from opening it. If it was ever freed, the Destroyer would have eventually consumed the universe. After the Vault hunters destroy the Destroyer, the Vault reseals itself and cannot be opened again for two-hundred years. The Guardian Angel reveals that in its home realm the Destroyer is indestructible, however it requires a host body to survive in this one and is vulnerable.
The Guardian Angel explains that she had known what the Vault contained and had guided the Vault hunters from the outset to protect the universe from the Destroyer. She expresses regret for the deception, but insists that it was the only way to ensure that the Vault hunters would be well positioned to defeat the Destroyer. As the story comes to a close the Guardian Angel is revealed to be a projected apparition from the Hyperion satellite 4N631 in orbit around Pandora, and then some distance away from these events a Claptrap is shown to be struck by a bolt of energy, its optic receptor changing from blue to red, and the Claptrap then rises and strikes a pose, reintroduced as an "Interplanetary Ninja Assassin".
In Borderlands: The Pre Sequel, it is revealed that Jack planned to use Angel to encourage the Vault Hunters to open the vault, and to ultimately obtain the Destroyer for himself and harness its power as a weapon. Jack obtained the Eye of the Destroyer and brought it back to Helios to experiment on. When force-fed Eridium, the Eye of the Destroyer can generate immense amounts of energy, which was focused into a super-weapon capable of destroying entire settlements, and was used by Zarpedon in the near-destruction of Elpis.
The opening of the Vault triggered the appearance of Eridium throughout Pandora. This event also gained the attention of Hyperion's President, Handsome Jack, who masterminded the events of the first game through his daughter, Angel.
- Simply entering the Vault completes the mission, Find Steele. In Playthrough 2 this unlocks access to a third playthrough-like setting where every creature in Pandora will be advanced to maximum levels, regardless of whether The Destroyer is killed or not.
- The planet of Pandora and its Vault are references to the story of Pandora's box from Greek mythology.
- The Vault Key and each of its fragments has certain texts:
- 1st Vault Key Piece (Sledge, Sledge: Battle For The Badlands): Sledge's chest contained this mysterious object.
- 2nd Vault Key Piece (Krom, The Next Piece): A low hum emanates from within, and it is warm to the touch.
- 3rd Vault Key Piece (Rakk Hive, Another Piece Of The Puzzle): This piece is cold to the touch.
- Complete Vault Key (The Destroyer, Bring The Vault Key To Tannis): This thing has certainly caused its fair share of trouble.
- The Vault's symbol is visible all over the human inhabited region of Pandora. It appears frequently in bandit graffiti, as well as on the face masks of bandits themselves. The symbol is used further in the sequels to Borderlands as a symbol representing countless vaults.