They look like sentient safes that run around, attempting to avoid being caught by the player. Razputin can open these with a PSI-Punch. Once opened, memories are revealed of the character whose mind the safe is in. Each Mental World has two memory vaults, with the exception of the Meat Circus, which has only one, for a total of nineteen in the game.
In each Mental World, one of the two vaults is generally in Raz's path when playing through the story. The second vault is in a less obvious spot. The combination of these memories provides insight into the backstory of each character.
The Psychonauts Vault Viewer app for iOS provides a way of viewing the memories outside of the game along with developer commentary.
- Using Clairvoyance on any Mental Vault will reveal they see Raz as a dog catcher.