I read a book quite a few years ago about a boy who is at school and is confronted by a guidance counselor who is a monster trying to kill him.
He is saved by a girl who has been watching him and flies him away to a land where his family used to live hidden in an unreachable mountain realm. There, he finds out that everyone has ancient powers, as well as his parents at one time; but the memories were altered to save their lives in the normal world
Also at this place there is a large reflection pool whose surface can be changed to show the past. This boy has a destiny to find something hidden by one of his ancestors