I am trying to find a book that I read back in about 95 or 96 maybe. It was a fantasy book ad the cover had a few different images each in their own frame I believe. I can only vaguely remember what it is about and am hoping someone will know its title. There is a boy who is the lone hero. His little brother is replaced by a changeling. At one point an invisible creature sit on him in his sleep trying to suffocate him. And the main villian has hounds that chase after the character. Sorry so little but I would greatly appreciate any help in finding this book.