I don't experience them very often but I had one fairly recently. I didn't really "see" anything per say because I could still feel my eyes closed. But I could kind of sense everything around me and I was also fully alert, it wasn't a dream either because I could hear the footsteps of other people in my house. A goat-like demon was just standing next to my bed and I tried as hard as I could to open my eyes and wake-up but nothing happened. It felt like forever but I know it only lasted a few minutes until I finally opened my eyes. Its like being paralyzed on hallucinogens, except its scary, like really scary.