As a kid I had a lot of nightmares because I was a retard who watched horror films and had a terrible fear of the darkness as a result.
Many of them involved running away from something without any hope at surviving, like a zombie apocalypse.
Ironically, my worst nightmare was the most tame — just me lying in my bed and hearing an unknown voice coming from my pitch black door, telling some story and growing closer. It freaked me out because everything looked too real and I never heard any distinct voices in my dreams before. The fact it might open the door and I see what it is scared the shit out of me. And what's worse, I couldn't force myself to wake up immediately, repeating the same thing with waking up to a voice starting to talk, again and again, barely able to move.
When I did wake up, I felt like a huge rock was lifted from my chest, and I could swear I saw some fucking transparent pitch black thing exiting through the ceiling of my room. After this I watched TV for a few hours because I was too scared to sleep or leave the room.
Looking back at this, I'm pretty sure it was just some rare episode of sleep paralysis but a ten-year-old me didn't know about such stuff at the time.