This dungeon in Liurnia of the Lakes is filled with poison, but it also offers an armor set and a pretty neat talisman.
Unique Rewards:
Grab the site of grace, then continue further into the cave. There’s a 
Golden Rune [3] on a corpse hanging over the edge in the first room — continue right past the corpse, and crouch as you near the next corner, as a bat is feasting in the alcove on your right. Kill the bat and immediately turn around, as a sorcerer is likely preparing a gross poison spell. Sprint towards him (making sure not to fall into the poison below) and take him out — if you move fast, the spell should miss. Once you start attacking him, two more poison sorcerers will start casting spells at you from across a small gap to the southeast. You’ll want to get a running start and then leap at them, and take them both out.
Past them you should see an even darker tunnel — slowly make your way down it, then pause once you enter the next room and look up — there’s a number of bats hanging out up there. If you have a ranged attack of some kind, use it to pull them towards you, otherwise walk slowly into the room until a few of them aggro. Back up into the tunnel to fight them to neutralize their winged advantage while fighting them. Going further into the right side of the cave will aggro a harpy — basically a much more dangerous version of the bats. She has a grab attack, so make sure you’re rolling if she dives at you. Once she’s down, grab all the loot in the room: A Golden Rune [6], the 
Sage Armor Set (three pieces), x15 Serpent Arrow, and a 
Golden Rune [5].
Go back out the tunnel you just came through and go left — you’ll encounter another sorcerer just around the corner. Continue hugging the left wall and see a spot where you can go left or right:
Continue going left, hugging the wall, and walk slowly into the dark area and target the ceiling — there’s a handful of bats up there. As usual, use ranged attacks if possible, and pull them back into the narrow corridor when fighting them. They’re guarding x5 
Glowstone on a corpse — grab them and then turn around and jump over the gap to the west where another sorcerer is probably already firing spells at you. Once he’s gone, you can go back the way you came to just before the bats and look down into the poison — its a 
Golden Rune [4], so feel free to grab it if you want (ideally only if you have a way to remove the poison effect). Then return to where the bats were, jump across to the west, and continue south and east into the next tunnel.
You’ll pass a Stake of Marika and then find yourself in a chamber where a few poison sorcerers are staring at the wall. You can sneak up and backstab each of them in turn, the continue down the passage — there are more sorcerers here, but none will aggro and you can backstab them all one at a time. Jump down the waterfall to collect the 
Poison Grease. Then use a 
Furlcalling Finger Remedy if you want to look for help, and traverse the golden mist when you’re ready to face the Cleanrot Knight.
