https://feldherr.org/2017/11/28/evil-high-priest-interview/
>I have nightmares quite often. During these nightmares, I don’t like them, but when I wake up, I remember them and often use them in my game ideas. A lot of Doom levels are based on nightmares I’ve had, for instance. Believe it or not, I have never had a nightmare in which Cthulhu figured. However, Lovecraftian elements are common.
>One of my recurring, and quite specific nightmares, also one of the most terrifying, is for me to be in an old house (often my grandfather’s or father’s), or an old library, and to discover that there is a small secret room there. This secret room is always small, and triangular, tucked into a corner of the building. It has a clouded window shedding a nasty yellow light over the interior.
>There are occult-looking papers and parchments scattered over an old desk, and on the floor, and old books laying everywhere. An overpowering musty smell is all around.
>As I look around this strange area, I become aware of movement in the corner. I turn, and a withered, hideous undead Thing rises up – the inhabitant of the secret room. Always mummified and awful, it reaches out a blackened claw towards me. I so far have always awakened before it touched me.
>This nightmare is so specific (it starts out general, can be in any building, and then becomes more and more specific towards the end), that my fear is sometime it might come true. Logically I know this is impossible. But nightmares aren’t about logic.
Funny that. Have any of you ever made levels based on nightmares you've had, or do you know of any other examples of when someone did?