I'm gonna just jump right in here with my thoughts. I have many.
Amber, The Psyche
Hallucination Amber is a little creepier than the live version of Amber that we knew in season 4. But she is merely a representation of House's subconscious, that has been manifested due to his feelings of guilt. To me, it is obvious why this has happened:
1) House is the master of guilt suppression. He regularly does things that the average person would feel incredibly guilty about. But House shoves that away deep inside his brain. That isn't to say that he doesn't feel guilty; it just...