You proceed into the Vault in an attempt to rescue Aymeric and confront the archbishop.
Special Character in Duty Support
The Vault can be completed with a special character if you use the Duty Support system.
How to Unlock
The Vault 4-player dungeon is unlocked by the level 57 Main Scenario Quest A Knight's Calling.
Reach the First Boss
Go forward through the large archway and the small metal gate. After you defeat the enemies that attack, go east through the gate that opened. Go north from there and defeat the enemies that attack. Beyond that, there is a Vault Deacon, and a large group of Ishgardian Bannerets attacks. After you defeat them, go north through the small metal gate. Defeat the enemies here, then go west and up the stairs to the boss's area.
Defeat Ser Adelphel
Attack Ser Adelphel, and after his health is depleted, he will double in size.
The tank should keep him facing away from the rest of the party to prevent him from hitting them with Heavenly Slash.
He will periodically hit the player highest on the enmity list with Holy Shield Bash, which temporarily stuns the player, and is followed by two hits of Solid Ascension.
Ser Adelphel periodically uses Holiest of Holy, hitting all players.
Eventually, Ser Adelphel uses Shining Blade, which places large white orbs around the area. These orbs will soon explode with Bright Flare, which will do damage and inflict Bleeding status on players nearby, so keep your distance from them to avoid getting hit.
Later in the battle, Ser Adelphel follows the Shining Blade attack by targetting a random player with Execution, a circle attack that follows the player. The marked player can move away from other players to avoid hitting them with the circle attack.
Reach the Second Boss
Go up the stairs to the next area. There is a chest in an alcove to the left. Defeat the enemies in this hallway and proceed onward. In the room ahead, there is a Treasure Coffer in the corner. Approach the east wall of this room and you will be attacked by two Faces of the Hero. They will periodically use Black Nebula, damaging all players in the vicinity. When they are defeated, go through the east door that opens.
The next area is straightforward, but with a White Knight and Black Knight at the end that will periodically use Black Knight's Tour and White Knight's Tour, a line attack at a random player.
Defeat Ser Grinnaux
After they are gone, enter the boss area. Attack Ser Grinnaux the Bull, and he eventually doubles in size.
He will cast Dimensional Collapse, an attack that marks several red-and-black arcs on the floor. Don't stand in these arcs.
Ser Grinnaux will target random players with Hyperdimensional Slash, a large red-and-white line attack. Avoid getting hit by this, or you will be knocked back.
An Aetherial Tear will appear at the edge of the area where the line attack hits. Don't stay close to these Aetherial Tears or you will be tethered and hit repeatedly with Dimensional Torsion, which places a stacking Vulnerability Up status on you.
Ser Grinnaux sometimes casts Heavy Swing on the player highest on the enmity list.
Ser Grinnaux will also periodically cast Faith Unmoving, knocking back all players.
He will sometimes cast Dimensional Rip, a circle attack that leaves a dimensional rip puddle on the floor. If a player walks through this puddle, they will take damage from Stellar Implosion and be inflicted with Heavy, and the dimensional rip will disappear.
Reach the Final Boss
Proceed west and you will encounter two more Faces of the Hero, as well as another Black Knight and White Knight in a room with a treasure chest. When they are defeated, go west through the door to reach the next area.
Up ahead, there is a treasure chest to the left. Go up the stairs and defeat the enemies, then go south. Attack the Vault Priest and he will eventually cast Summon Familiar, summoning four Cathedral Gargoyles. They will each periodically cast Horror's Eye, a large circle attack.
After they are defeated, go east, and then north up the stairs to where the final boss awaits.
Defeat Ser Charibert
Ser Charibert will sometimes cast Altar Candle on the player highest on the enmity list.
He will sometimes cast Heavensflame, creating a temporary fire puddle in the area.
He will sometimes cast Altar Pyre, which damages all players.
He will sometimes tether two players to each other with Holy Chain. If you are chained to another player, run away from that player until the chain breaks.
Ser Charibert sometimes summons untargetable Black Knights and White Knights along the north edge of the area. They will march southward, and if you are in their path, you will be hit by Turret Charge and be inflicted with Bleeding status.
At about 50% health, Charibert disappears, then becomes untargetable along with a Dusk Knight and Dawn Knight, which will cast White Knight's Tour and Black Knight's Tour, line attacks that inflict Slow and Bleeding. He will create eight Holy Flames around the area. Players should kill the Holy Flames as quickly as possible, because each one that is still there when Charibert casts Pure of Heart will explode with Sacred Flame, hitting all players. If too many Holy Flames are left alive, the party will not survive.
If you survive this attack, the battle resumes. Continue attacking Ser Charibert and avoiding his attacks as before, until he is defeated.
Completing the Quest
Defeating the boss will complete one of the quest objectives for the Main Scenario Quest A Knight's Calling. There will be a cutscene. This one is very important, so it is recommended to watch it either now or via the Unending Journey in an inn room.