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Bad moon falling.
— In-game description

The Great Vault is a massive set of Eridian ruins located in the barren desert of Pandora. It is the site of where Pandora, the actual Great Vault, can be opened, and requires the use of Elpis as its key to open.


This is the location of the Vault of the Architects on Pandora, and where the fight against Troy Calypso takes place. 



Story Missions

Points of Interest

Dig Site

The Dig Site is a small area where the Children of the Vault performed some of the many excavations in search for the opening site of the Great Vault. There is a Fast Travel station just before the drop into the arena where Troy Calypso is fought, as well two vending machines for ammo and health.

At the bottom of the Dig Site is a diamond-shaped arena where Troy Calypso is fought. At the edge of the arena is a massive inactive Vault, which the Calypsos utilize to draw Elpis closer to Pandora, all while charging it with Troy's phaselock powers in order to open the Great Vault and unleash The Destroyer. Once the battle against Troy is finished, an exit Fast Travel station will become available to use at the back of the arena.

Vault of the Architects

After defeating Troy, the inactive Vault will become active, allowing the Vault Hunters access into the Vault of the Architects. According to Tannis, it is not the actual Great Vault, as the Calypsos were in possession of the Pandora Vault Key for sometime and could have easily opened the Vault ages ago, theorizing that the power within the Vault was in fact knowledge that the Calypsos were already in possession of. Inside the Vault are four white chests, as well as the Eridian Analyzer, a device capable of allowing its user to decipher the Eridian language.


  • The in-game description presumably references the song Bad Moon Rising by Creedence Clearwater Revival.
  • Title given by the game is "Eridian Ruin".
  • Due to the nature of the Great Vault, this is not actually the location of the Great Vault itself, but (judging from the name of the Vault that the Vault Hunters enter upon defeating Troy) rather a Vault created by Eridian architects of Pandora itself.