This is perhaps the most annoying room in the entire game. You enter on the West side and the corridor balloons to a larger, round room in the middle before narrowing back to a corridor at the East side. In the large center part of the room are nothing but sleep fields and two Reapers, one at the North, and one at the South.
Unless you have a Mage in your party who has benefitted from all the Orbs encountered in the dungeon so far, you can expect to have your party members falling asleep quite regularly as you attempt to take out the Reapers, who are casting Sleep auras themselves.
Fortunately, there is nothing more to this room, so you shouldn't have much trouble, aside from the annoyance of your heroes constantly falling asleep.