You trouble with auditory hallucinations and schizophrenia, these two combining and forming a shadowy-like man, you started to call this shadowy-man "Illusion", to try and deny his existence. He began to follow you everywhere, not just your home, but school, work, the park, everywhere you went, he followed you.

Illusion: Watching your every move, not saying anything you could hear, but he was whispering, which was driving you insane