Once the Covetous Demon is down, head through the doorway on the side, and up the stairs to find another bonfire and Lucatiel. Speak with her to obtain the Ring of Steel Protection +1, then head into the next room and up the stairs on the left. Take out the three enemies and pick up the Radiant Lifegem in the far left corner.
Continue through the doorway and over the bridge, stopping when you reach the huge gear. Fight the mage knight ahead while hiding behind the gear to block the attacks from the archers across the way. Head into the room ahead, and you'll find a hallway on the right and a ladder on the left.
Go around to the right and into the hallway. Pull the lever, then continue down the stairs and kill off the enemy to the right. When you reach the room ahead, go left to find a chest at the end which holds a Pike. Collect the item, then head back to the room you just left and approach the ladder at the end. Two enemies drop down just before you reach the ladder. Take them out, then climb the ladder.
Kill the enemy at the top, then through the mist door to find a bonfire. Light it, then light a torch and head back out and up the makeshift ramp to the right that leads to the windmill. Watch your step to make sure you don't fall off, and light the windmill on fire with the torch. This drains the poison out of the area and makes the upcoming boss battle much easier.
Head up the next set of stairs to find three Black Firebombs. Watch out for the lever on the ground right next to the item. This is another trap that shoots darts if you step on it. There's a ladder in the middle and a balcony outside, but before you head in either of these directions, move to the other side of the area to find another enemy and a Manikin Mask, then head outside to the balcony.
Defeat the enemy on the balcony, then break the wooden railing near the entrance and walk along the ledge to the left. Laddersmith Gillian is waiting at the end of the ledge. Speak with him and purchase a ladder for 2,000 souls to gain access to the area below and obtain a Pharros' Lockstone and Twinkling Titanite. He then moves to Majula and can be used to build a ladder down the large well if you haven't been down there yet.
Go back to the balcony and head all the way to the end to find an item just beyond the wooden railing. Cut down the railing and pick up the item to obtain a Simpleton's Spice. There's a lever at the end of the balcony which raises the platform to the right. Under the platform is the Soul of a Proud Knight and a Divine Blessing, but the platform doesn't stay up very long, so be quick to grab the items before the platform returns to its original state. Then pull the lever again; this time hop onto the platform before it moves. Open the coffer at the top to obtain a Mirrah Shield.
Drop back down and climb up the ladder next to the platform, then head down the hallway to the right just before you reach the mage knight at the end. Speak to the man in the room below, then head back up to the hallway and take down the mage knight, remaining cautious of the poison pots. Continue up the stairs to the left, and kill the mage knight and two pyromancers at the top. Open the coffer, which is trapped with poison, to find a Pharros' Lockstone.
Head back down the stairs and continue straight to find another pyromancer. Kill the pyromancer with ranged attacks, then prepare to make a tricky jump to the other side of the platform. Jump at the last moment, and aim for the left side of the platform ahead to give yourself the best chance of making it across.
Pick up the item at the edge of the platform to obtain a Radiant Lifegem, then open the coffer at the end to find the Soul of a Brave Warrior and Crimson Water. Before you jump back across, note that there's an item on the bridge below. If you wish to obtain the Poison Broadsword and Human Effigy, stand where at the position where the item on the platform was located, then fall straight down. Jump across to the platform against the wall, then make your way to the left, then up the stairs to find yourself on the same floor you originally entered.
Make your way back up to the area with the ladder in the middle that leads out to the balcony. Climb up the ladder, head into the hallway on the left (the one with the pot in it), then continue up the stairs to the left. At the top there are two pyromancers and a mage knight. The pyromancers are standing next to poison pots, so be careful when you attack them so as not to smash the pots. Defeat the enemies then head around the corner and up the stairs to the right to take down another pyromancer.
Two mage knights guard a doorway on the other side of the room. The doorway eventually leads to the boss, but before you engage them, go up the stairs on the wall near the middle of the room. To the right are several poison pots. Carefully destroy the pots, staying at maximum range to avoid getting poisoned.
Behind the pots there are several poison bugs. Take them down before they can gang up on you in order to avoid the brunt of their poison gas attacks. Once done, do not open the chest. Instead, pick up the Smooth & Silky Stone in the corner, then attack the chest in the middle. Kill the chest to find a pair of Dark Gauntlets and a Work Hook.
Ignore the Pharros' Lockstone on the face up the stairs and leave the room. Continue up the next set of stairs to fight the invader. Defeat him to find Brigand Gauntlets +5. At the end of the hallway ahead, go right and interact with the wall on the right. You won't see an on-screen indicator, just press the button as if there were an item to pick up.
Behind the hidden wall is a bonfire. Light it, then head to the other side of the platform and do the same to the wall there. Behind this hidden wall is a chest that holds a Petrified Something. Head back down the stairs to the room below and take down the two mage knights guarding the entrance to the boss. Pick up the Poison Stone in the corner, then head up the stairs and through the mist door to engage Mytha, the Baneful Queen.
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