Oh god, the whole concept of waking up in a building with no windows, no doors? While one would get used to such a thing, the idea of having no way out can cause people with isolation issues some serious lack of sleep.
Moonlit Whispers examples:
Garth is recording the noises at night, when he sleeps. Mainly, it's his neighbor's television set. But when the television set goes off, something else can be heard. Listen to the end of this audio and then proceed to crap your pants.
Closest to the Sun examples:
The sheer mindscrew that Achromatic Morality goes through within the Empty City is terrifying. Also the fact they she apparently wrote 417 posts, though only four show up. The Empty City messes her up so much, the post begins like this:
I have sinned. I must be punished.
This place is warped and ti it twisted and I can't see the wood for the trees. II ma wronged and must be punished.