Final Fantasy XV – How to get Vault Key (Secret Endgame Dungeon Key
First you have to complete the main story, save your game and return to the main open world for chapter 15.
Complete the following 4 dungeons. Duarell Caverns, Balouve Mines, Castlemark Tower and Crestholm Channels. These Dungeons count as completed after you found and beat the final boss.
After that, you can collect the vault key from Ezma in “Meldacio Hunter HQ”. She is an old woman who will give you the vault key after you finished the 4 dungeons.
This will open up 8 new hunt missions deep inside the dungeons. The vault key opens all 8 vault doors in these dungeons.
The are the new endgame dungeons
Keycatrich – Level 55
Grotto – Level 65
Fociaugh – Level 65
Daurell – Level 72
Balouve – Level 78
Steyliff – Level 86
Crestholm – Level 92
Costlemark – Level 99
YOUTUBE PLAYLISTS (Final Fantasy XV)