The horror I understand is a kind of artistic conception, which you can only experience in dreams. It is deep and settled, even in the movements. The reason why I feel psychological trembling is that I cannot escape.
In the foggy, dark and quiet time and space, you are standing next to a pool of water with no visible edges, no protection, and only one person wide. The water is a deep blue, and everything is very quiet. A huge, completely black fish, as big as a ship, swings its tail, and there is no way to escape from the pool beside you. There is no sound, no change of light and shadow.
Or a whole side of endless grassland, full of green grass, maybe stones, and small white flowers, followed by a group of people, zombie-like people, making no movement, no sound, not stopping for even half a second, chasing you on this endless, unobstructed grassland. You can escape, but you can fall into danger every second.
Conception: