Continue along the path and up the staircases until you reach a room with three enemies and three newly defrosted Frozen Golems. That trio is protecting a treasure chest. You'll need to kill an enemy near each to wake them up and defeat them.
Eliminate the two Sorcerers and the Retainer and then take on the Frozen Golems. Use all of the available space, including the rooms and the staircases, to fight them.
Open the chest and collect Curved Nil Greatsword x 1, which has the peculiar property of getting stronger with each New Game+.
Head down the hallway that was once blocked with ice, kill the Sorcerer and the Retainer hanging out there, plus the two Frozen Golems, if you awaken them.
Open the iron gates around the corner and recruit another Knight of Eleum Loyce.
Walk up the staircase behind the chair he was sitting in and open the black door to reveal a shortcut to the area where you fought Aava, the King's Pet and the Outer Wall bonfire.
Exit the knight's room, turn left and follow the path around a corner. Pillage a corpse at the end of the hallway for Flame Butterfly x 3.
About halfway back down the hallway that you're in, on the wall opposite of the corpse, is an illusory wall. Walk along the wall hitting the action button until you find and open it.
Drop through and continue forward with the doorway that you entered through at your back. Kill two Rampart Golems and a Sorcerer in the hallway.
Walk out to and off of the balcony and onto the bridge below. Defeat the Crystal Sorcerer waiting for you, turn left into the room beyond the bridge and open the treasure chest to collect the Twin-headed Greatbow x 1.
Turn around, drop down off the ledge and retrace your steps back to the hallway with the illusory wall. Drop down, turn around and ascend the staircase, where you'll have to fight a Crystal Sorcerer stationed there. At the top, open a chest to collect the Fire Clutch Ring x 1, which increases fire attack.
Hop off the ledge next to the treasure chest, and you'll find yourself back in the room where the Frozen Golems protected the treasure chest.
Use an item to warp to or take the path behind the Knight of Eleum Loyce and follow path to the Outer Wall bonfire to rest up and continue your quest.