Go forward and turn right into the corridor. After going up a few of the stairs, a short cutscene will start. Continue up the stairs, there will be spiders here so be careful of these. There will also be two red Mind Flayer Phantom on these stairs to contend with. The Mind Flayers will be separated from each other. At the top of the stairs, on your left is a Fog Wall.

Prepare for the boss battle with Old Monk!