At the end of some Dungeons there will be locked vault doors that when unlocked will lead to secret endgame dungeons that have higher level enemies and better rewards. There are eight locked vaults in total that lead to endgame raids and they are listed as follows.

Balouve - Level 78.
Costlemark - Level 99.
Crestholm - Level 92.
Daurell - Level 72.
Fociaugh - Level 65.
Grotto - Level 65.
Keycatrich - Level 55.
Steyliff - Level 86.