You light your torch and lantern and make your way down the spiral staircase. Eventually, you reach the sewer systems. The tiles are covered in patched os slime and mold here and there and murky water runs runs in a central canal. The sewers are not as dark as you expected thank to light shining through grates at street level.
On the walls are sconces to put up lit torches in, and you notice burnt out torches in the sconces on the walls of the passage leading north.
Fog of War map. I've taken into account Malingad's and Nunri's Night Sight, humans will see only the 3m radius around the torch and lantern (with each square being 2 meters).
You can all make a Perception check at that point.