While I was at college, I lived in a dorm where most of the beds were elevated on A-frames to within a couple of feet of the ceiling. This was done to allow more space within rooms, since they were quite small to start with. One night, during my freshman year, I fell asleep in my bed while my room-mate worked at his desk, tucked below his bed at his desk on the opposite side of the room.
I remember dreaming that I had found a very old piece of vellum with what appeared to be an Enochian Chant written on it. These chants were used in the Middle Ages to summon angels, and are beautiful pieces of vocal composition. I began to sing the chant (confirming that this was a dream, because I cannot read music, much less hold a tune). When I got to the end, I was disturbed to find that I had just sung the chant to summon Lucifer.
Sometime later, I was lying on my stomach awake in the dark, and I felt something approaching. When I picked up my head and looked, a great big bat landed on my face! With a start, I woke from that dream, to find myself back at in my room, with my room-mate's desk light still on, but with him nowhere to be found. Instead, sitting on the end of my bunk bed was a very old, wrinkled man, who held out a bony, freckled hand. He said, quite pleasantly, "Shake the hand of Satan."
I watched with amazement as my hand moved out to grasp his -- without my being able to stop it. And then it was all gone, and I woke up the next morning. I asked my room-mate whether he had noticed anything strange the night before, and when he replied that nothing had happened, I explained my dreams. He told me he had not left the room at all, and had gone to bed quite soon after I had last spoken to him, turning out his light.
I tried to convince myself that this had all meant nothing, but I did spend the next days wondering about that handshake. I had a very creepy feeling that I had just done something that would not do me very well in the near future. Luckily, nothing did happen, and I was able to file this event away under "strange (nested) dreams," but I often wonder what would have happened to me mentally had some other strange chance occurrence come to pass while I was affected.
Should I ever find out that such an Enochian Chant exists, I will be sure never to read it.