In my early childhood I was subjected to intense night terrors. I remember these clearly, but the concepts can barely be rendered into words. They weren't movies of images like other dreams, they were more like pure emotions, combined with sense-free apprehension of states which didn't map onto ordinary experience as I had known it to that time. Compared to later drug experiences
they seem less strange, but when you are a child you assume that anything dangerous will be explained to you. Anything which hasn't been explained and made known is dangerous.
The worst nightmare state was like a hyperawareness of the laws of physics or the basic state of the world, combined with absolute knowledge that it was all wrong. It was as though I were an alien creature from a reality with laws radically different from our own, who had been suffering from amnesia. The amnesia might have been an adaptation, a way of coping with these new nonsensical laws of cause and effect. The only way I could adapt was by forgetting the way things should have been, so I could deal with the way things now were. However, in the dead of night, in my sleep, the old laws flooded back into memory and I would awake screaming and terrified at the feeling of disorientation. It was as though I came from a world where gravity was a repellent force, and was frightened at being in an enclosed room this close to large mass of the earth, because I knew that I would be flung away at great speed. Or, a reality where the geometry didn't allow for objects to enclose other objects, and the fact that I was inside the house was an impossibility which was driving me mad. Or a reality where consciousness was entirely divorced from solid matter, and the body to which my mind was so firmly attached now was like waking up and realising that a decaying dead goat has been grafted onto your side while you slept. These states were exquisitely terrifying, beyond the fear which imminent death might inspire. They were terrors which transcend extinction, terrors based on concepts and scales which far outweigh mere existence.
In the fiction of Lovecraft he often mentions cities and buildings with non-Euclidian geometry and the effect that gazing upon same has upon the sanity of his human characters, but the denizens of those cities would feel the same horror when exposed to our own architecture. I felt like a lost Shoggoth imprisoned in a human body suddenly remembering the shapes and forms of my home, and apprehending the wrongness of my human home.
I remember some details. In one particularly horrifying dream I found myself in a comforting space of absolute blackness, but there was something else there with me. I could perceive it as a point, not so much an object, more a point of space with certain qualities. It moved in loops around me, not moving so much as altering the space before it and restoring the space behind it so that it's intrusion into this space appeared to be moving. It was important in the logic of this nightmare to make such distinctions. I struggled for some time to perceive what was happening, and why this impurity was infecting velvet blackness. The thing that set me screaming was when I hit upon a visual model in the form of a coloured trail which marked where the point had been. Suddenly I was surrounded by a tangled fence of neon coloured lines, and I could "hear" the point moving, buzzing like a motorcycle engine. When I woke up I explained the dream as being trapped by a motorcycle circling around me, which made sense and was the only way I could render it into words. It wasn't so much being trapped by the trail of vectors left by the intrusion point, as being appalled at the circularity of its movement, and powerless to banish it.
Another. Fine white particles drift across a grey background formed by an infinity of fine white particles, rendered stationary by distance. The particles move in the same direction, at the same speed. In fact, it would seem logical to declare that my point of view was moving and the particles were stationary, but I know that I am the stationary point. This seems infinitely comforting. Suddenly a troubling thought - which direction are the particles moving? My horror grows as I realise that to ask such a question equals a kind of metaphysical blasphemy. I feel a sinking feeling of loss, a fall from grace. The purity of the movement of the particle field decays. Now it's just drifting snow, or falling sleet, or rising ash. The concept of absolute direction decays this miracle vision like a blight. It fades and dies.
One effect which lasted into later life was a hypnotic dreamlike state where the rules of scale seemed to alter. The night room seemed to become gigantic, as though the ceiling was millions of light-years away, and my consciousness shrank down to a point peering up into a titanic space. This state would come upon me at different times, usually when I was tired or stressed. It wasn't frightening, at least not in adulthood, and it often helps to put things into perspective. It acts as a reminder of the truth of scale and the true insignificance of life.