After Ursandel asks you to put an end to Lady Amandine's madness, you enter Haukke Manor.
How to Unlock
The Haukke Manor dungeon is unlocked by the level 28 Main Scenario Quest Skeletons In Her Closet.
Haukke Manor Ground Floor Map
Find the Green Key
The Manor Maidservants throughout this dungeon will cast the circle attack Dark Mist. The tank can interrupt Dark Mist with Interject, or the Ranged DPS (if any) can interrupt it with Head Graze. If you stand in the Dark Mist attack marker, you will be inflicted with the Terror status, which prevents you from doing anything until it wears off. Be sure to kill Manor Maidservants before other enemies, and avoid standing in their attacks.
Go south, then into the east room to find a Tiny Key. Leave that room and make your way clockwise through the area, and go north into the room there. Unlock the Locked Door and go through, then kill the Manor Maidservant and take the Tiny Key there. Then go south and make your way clockwise around the hallway. When you see a room on the right with a purple glow at the door, go through to reach the first boss.
DPS should use Limit Break on the Manor Claviger as soon as possible.
The tank should turn the Manor Claviger away from other players so they won't be hit by the Sweet Steel cone attack, which is not marked by an orange ground marker. The Manor Claviger will target random players with the Void Fire II attack. Step out of the attack marker to avoid it.
She can also cast Dark Mist, an uninterruptable circle attack centered on her that inflicts Terror. Players inflicted with Terror will be unable to do anything until it wears off.
After she dies, pick up the Green Key.
Find the Yellow Key
Ignore the door that opened behind the Manor Claviger, and instead go west and unlock the Ivy Door, then go down the stairs. When you reach the bottom, pick up the tiny key at the base of the stairs, then go east into the dungeon area.
Haukke Manor Cellarage Map
Most players will want to ignore the path to the south of the Carnation Door, which has a Tiny Key. It is just there to allow you to get all of the treasure coffers.
So instead, go clockwise around the dungeon area. If you don't have any tiny keys, you can go into the north middle room to get two of them.
Continue going clockwise around the area until you reach the south middle room. Use a tiny key to unlock it, and pick up the Yellow Key there.
Find the Bloody Parchment
Go west over the one-way ramp, then go north to the Carnation Door. Check on it to use the Yellow Key to unlock it, then go inside.
Manor Jester and Manor Steward
If there are ranged DPS in the party, one of them should use Limit Break on both the Jester and the Steward as soon as possible. If there are no ranged DPS in the party, then a DPS should use Limit Break on the Manor Steward as soon as possible.
Kill the Manor Steward first. It can cast Soul Drain, a circle attack centered on itself.
After you kill the Steward, focus your attacks on the Jester until it is defeated.
Pick up the Bloody Parchment, open the treasure chest, then all players should interact with the Aetherial Flow to return to the entrance of the dungeon.
Defeat Lady Amandine
From the dungeon entrance, go up the stairs and check on the Sealed Barrier, and say Yes to use the bloody parchment to remove the barrier.
Go up the stairs. Most players will want to skip the optional area to the south, which just has a locked door and a treasure coffer with a random weapon inside.
Back at the top of the stairs on the Second Floor, you will find a Manor Sentry. Attack it until it flies away at about 50% health.
Go through the door to battle Lady Amandine. Throughout the battle, Lady Amandine will cast Void Call, summoning an untargetable Manor Sentry. The Sentry will cast Petrifying Eye, a gaze attack. All players should turn their characters to face away from the Manor Sentry before it finishes casting Petrifying Eye to avoid the attack.
Later, Amandine uses Void Call to summon a Lady's Handmaiden, which can cast Stoneskin on Lady Amandine, increasing her defense. Focus all attacks on the Lady's Handmaiden until she is defeated, then resume attacking Lady Amandine.
Amandine can cast Beguiling Mist, an unavoidable attack that temporarily inflicts all players with the Seduced status, making all players walk toward Lady Amandine. This is accompanied by a Manor Sentry casting Petrifying Eye. As soon as the Seduced status wears off, be sure to turn your character away from the Manor Sentry.
Void Thunder III is a high-damage attack on the player highest on the enmity list. The tank can interrupt this with Interject, or the Ranged DPS (if any) can interrupt it with Head Graze.
Completing the Quest
After you defeat Lady Amandine and leave Haukke Manor, there will be a cutscene.
This will complete one of the quest objectives for the Main Scenario Quest Skeletons in Her Closet.