Timeless Wallow is the Gilded dungeon in The Parch for Night Market. Gilded B'Kyfxi is the only boss.
Three elite adds spawning throughout the fight, and then a second phase starting at 45%. Focus the adds, avoid AoEs, and outheal the Baneful Mark.
Keep B'Kyfxi faced away for Mind Blast , keep killing Malicious Spheres before they charge, and block, dodge roll, or don't get hit by Tentacles . At 85%, 70%, and 55%, B'Kyfxi pauses to summon a Bone Wyrm with skeletons, so focus the Bone Wyrm, interrupt the archers, and avoid Cold Snap . At 45%, she gains access to Crushing Darkness , Nocturnal's Favor , and Baneful Mark , but doesn't summon Bone Wyrms anymore.
Cleave
B'Kyfxi's light attacks cleave in front of her instead of only hitting the tank. If the boss is turned into the group, anyone standing in front gets damaged.
What to do
Tank keeps the boss faced away, everyone else stays out of the front.
Orbs that stun when not killed in time
Malicious Spheres roam around the room and can be killed. If a player walks into one, it explodes, stuns, and sends more beads outward. If left alone long enough, the sphere will eventually charge on its own.
What to do
Kill them. If one does charge, break free and outheal the damage.
AoEs
Tentacles swipe at players and leave extra AoEs in the room.
What to do
Block, dodge roll, or get out of the AoEs.
Elite add at 85%, 70%, and 55%
At 85%, 70%, and 55%, B'Kyfxi summons one Bone Wyrm plus skeletons, including 2 archers with interruptible channels and melee skeletons.
What to do
Focus the Bone Wyrm and interrupt the archers.
Cone AoE with gaps
The Bone Wyrm uses Cold Snap, a cone AoE with gaps inside it.
What to do
Block, dodge roll, or stand inside the gaps.
Heavy attack which spawns adds
The Bone Wyrm's heavy attack projectile spawns 2 scarabs on the tank's location. If they get too close to you, they shred your armor.
What to do
Cleave them down. Snare them if you're struggling with outrunning them.
Second phase
At 45%, B'Kyfxi enters Shadow Form and now uses Crushing Darkness , Nocturnal's Favor , and Baneful Mark .
Kite
Crushing Darkness always goes on the tank and can be blocked or dodge rolled, but its damage ramps up over time, so it is better to kite it left to right and dodge roll whenever you have to move through it after running out of space.
What to do
Kite.
Heavy attack
Nocturnal's Favor is a heavy attack projectile that cannot be dodge rolled and can be extremely deadly if a Malicious Sphere stuns you right before it.
What to do
Block.
Healing debuff
Baneful Mark lowers your health, doubles your Ultimate cost, and then applies a healing debuff. Tanks should use damage shields because any damage that hits real health while Baneful Mark is on you is extremely costly to outheal.
What to do
Heal it immediately. Tanks should use damage shields so any other damage does not hit real health while Baneful Mark is up.
Defeating Gilded B'Kyfxi will grant you the following buff:
Abyssal tendrils join from the void! When an abyssal tendril spawns, three Pearls will appear. Each Pearl you collect shields you from 33% of incoming damage. The tendrils will attack any enemies near them and heal you when you stand near where they spawn. Sand Swipe only lasts 15 minutes and only takes effect within the bounds of the Night Market.
Footage from the dungeon is below.