He looked around, keeping his sunglasses on knowing that he would pay for it if he didn't. He could still see perfectly clear, like he was in a lit area for a human. He said," yes, but now I'm in my environment. And my knowledge that this is an illusion helps me. Besides, I can do this." He took the darkness that was around him, and manipulated it into a solid wall, blocking the monsters and ghouls from him. Due to this being an illusion, he actually created a wall of solid darkness in real life, having used the shadows from the surrounding area. 

( I'm not to sure how that would cause an effect, so I went with that.)