I call the blackness the void. I have a part about this in my tutorial about Dream Stabilization (that is still awaiting approval)...which is really interesting because I hadn't seen anyone else suggest linear acceleration before while inside the void. In my tutorial I explain how this can be used to enter a new lucid dream. Basically you start moving forward, accelerating linearly through the darkness, getting faster and faster. Eventually you are flying so fast through the darkness that it breaks the fabric of the void and you will suddenly find yourself entering a bright lucid dreamscape. I have used this quite a few times. One time however...and this was really strange...when I was accelerating through the void...something invisible with strong hands and sharp fingernails grabbed hold of me and would not let go. I had to fight it off all the way back out of the dream and into my bed. Creepy, eh?