You're walking home one day and BAM! somebody hits you in the back of the head. When you wake up, you are strapped down to a chair, in a dimly lit room. Sitting infront of you is a guy with a weird goatee. He says the following to you:
"Well hello, there. Now, don't be afraid, I'm only a psychotic psychologist. Get it? Hah! Now, I apologize for the incident earlier regarding knocking you out. But there really was no other way to get you to agree? I mean what was I supposed to say, 'Hello, child, would you like to be part of a psychological experiment where you could die?' I didn't think so either. How did it feel to be knocked out? Do you fear the dark? I hope not. I know you can't see me right now, but I don't care. By the way, I really like drinking as well as rescuing koalas. Did you know I saved a whole family once? I think I've had too much wine! Just answer my questions. What is the answer anyways? Do you fear the dark? I think its light indeed. Hee hee hee hee hee. I'm crazy, I know. Now, there is no reason to be afraid. Maybe you shoudln't trust me. Here's what it is: I ask you a question, and you tell me the most obvious answer. The one that fills your brain, screaming at you telling you its the right answer. You don't have to panic, all you have to do is agree. Now your a pretty bad child, that's why I picked you. No one would ever want you after all. Any how, here's the little riddle you have to solve. Solve it, and I'll free you, don't solve it, and I'll kill you.
I'm the fastest thing in the universe.
Nothing can ever catch me.
I engulf the shadows,
I can get pretty hot, too.
I break at dawn,
Make you blind.
I am a void,
I am empty.
Fill me up and destroy me.
I am nothing.
I blind your sight.
I am _____
What am I?"
How do you survive from this maniac?