One of the worst experiences I can remember happened when I was extremely young. I don't recall exactly when this happened, but I remember it was before I started attending kindergarten. When I was very young, I would often get up in the middle of the night and climb into bed with my parents. I'm not sure if this was because of fear or loneliness. I don't remember many things from my young childhood, but this memory is still very vivid in my mind.
One night, as usual, I got up and went to get into my parents' bed. I remember that I was getting comfortable lying on my back right between them. Above the head of the bed was the only window in their room. They never bothered putting curtains or blinds on it because it was high enough off the ground outside that no one would be able to just walk up and see into the room. As I lay there, not yet falling asleep, I heard heavy footsteps outside the wall at the head of the bed. I looked up at the window and instantly froze in fear. I heard the footsteps getting closer and louder until I could feel them vibrating through the bed. I finally saw what was making the noise step in front of the window.
At first, I could only see a dark figure against the cloudy sky above. Then, it turned toward the window and looked in. It was a humanoid figure as far as I could tell. All I could see from my angle were its shoulders and head. Its head did not narrow down to a neck before reaching the shoulders. It was black and stood out very clearly in front of the cloudy sky in the moonlit night. It seemed to be very solid and not hazy like some people describe as "shadow figures." Its eyes were red and glowing with a shape that I can only describe as wicked and evil. It looked down at me and I was frozen in place looking directly up at it. After a few seconds that felt like an eternity, I saw its mouth open and the same red glow that lit up its eyes flowed out, and then I heard its voice. It didn't say any words, it only moaned long, loud, and full of bass. I finally snapped out of it enough to throw the covers over my head. I could no longer see anything and could only hear it finishing its long moan and my panicked breathing. I never heard it walk away. The next thing I remember after that was waking up under the covers. My parents were both already up and the bright sunshine coming into the room blinded me when I threw the covers off.
I never actually saw it in the physical world again after that, but it plagued my dreams for years to come. I had recurring dreams that anytime I looked at a window with no curtains or blinds covering it, I would hear the footsteps again. It would always come to the window and look for me. I would hide the instant I heard the footsteps and I don't recall any dreams where it actually saw me. I do remember that anyone else in the dream would not notice the footsteps or the giant, black, red eyed beast staring through the window. Thanks to the constant nightmares, I developed a fear of windows that lasted through most of grade school.
I've seen several stories now describing something similar terrorizing others, sometimes even being in the same room as them. It makes me feel almost lucky that this was all I got, but it was still the most traumatizing experience I remember from my young childhood.