 These people have these experiences in which they wake up in their dream and feel they can't move. And then they have a sense presence, a lot of them, where there's an entity in the room with them. The entity is often amorphous. It's hard to see what it is exactly. It's kind of like often a dark black or dark gray figure without a face. In the Middle Ages, people described this as incubi and succubi. These are demons.