|The following is based on Fallout Shelter or Fallout Shelter Online and some details might contradict canon.|
The Mystery of Vault 666 is a single-stage quest in Fallout Shelter. This quest is obtained from a quest clue, which can be found during an unrelated quest. After the dwellers return to the Vault, the quest will be available in the Overseer's office.
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|Opening message||Dweller response||Character response|
|Mu ha ha ha ha!|
So! You have discovered my lair! Vault 666! I am...
|Put a sock in it, you second-rate supervillain!||Who you callin' second-rate?|
|A hidden Vault... Why you little devil...||You have no idea.|
|Go to... Well, you know!||I'll meet you there!|
|Really? Vault 666? El Diablo?||Everyone's a critic.|