Lanterns with no apparent power source are fitted to every surface in room 9/22, casting off light and excess heat in a way that minimizes the ability for shadows to exist in the room. The light and heat is so much that any adventurer who spends a turn in the room must make a saving throw; on failure they are blinded and take constitution exhaustion as the light and heat overwhelm them.
The lanterns can be broken, but if not done quietly the action attracts the attention from the bound elemental servants of the Brass Lens.
I'm going to make a mental note to come back to this one down the road. I think the idea of an overwhelmingly bright room as a hedge against the shadows next door fits here, but I don't think I implemented it well, or that I will implement it well anytime today. Work has turned my mind into mush and I have a D&D game to run in about an hour.