The Mystery of Vault 666

 is a repeatable quest in Fallout Shelter.

Synopsis
''While adventuring, a Dweller discovered a map to Vault 666. It's not on any official Vault-Tec registry. What secrets could it hold?''

Objectives
''Vault 666 isn't on any official Vault-Tec registry. Time to investigate.''

Dialogue

 * Who you callin' second-rate? (_Conversation_1_NPCEnd_1);
 * You have no idea. (_Conversation_1_NPCEnd_2);
 * I'll meet you there! (_Conversation_1_NPCEnd_3);
 * Everyone's a critic. (_Conversation_1_NPCEnd_4);
 * Mu ha ha ha ha! (_Conversation_1_NPCStart_1);
 * So! You have discovered my lair! Vault 666! I am... (_Conversation_1_NPCStart_2);
 * El Diablo! (_Conversation_1_NPCStart_3);
 * So tell me... Are you ready to burn?! (_Conversation_1_NPCStart_4);
 * Put a sock in it, you second-rate supervillain! (_Conversation_1_Team_1);
 * A hidden Vault... Why you little devil... (_Conversation_1_Team_2);
 * Go to... Well, you know! (_Conversation_1_Team_3);
 * Really? Vault 666? El Diablo? (_Conversation_1_Team_4);