Exit the balcony with the bonfire, and kill the Retainer in the hallway. Head to the the opposite end of the hallway and peer into the next room. It used to be filled with enemies and ice. Now it's filled with more enemies, chipped ice and chests.
Inside, you'll find two Retainers, two Sorcerers, one Crystal Sorcerer and a Mimic. There are also two Frozen Golems, one on each side of the room. If you kill an enemy near one, it will spring to life. They do devastating amounts of physical damage, but they also reward copious amounts of souls.
As usual, enemy management is key. Whenever possible, enter with caution and convince your enemies to follow you out of the room and back into the hallway by the bonfire, so you can take them out not as a herd, but in small numbers.
Once everyone's down, open the treasure chest and collect Twinkling Titanite x 3 and Petrified Dragon Bone x 3. Note that the treasure chest on the lefthand side closest to the door from which you entered the room is actually a Mimic.