The art is simply lovely. I like your worn but still young-looking Dumbledore, and your cocky Filch... before the kids at Hogwarts have left him cynical and grouchy.
Yet, in the story itself, both Dumbledore and Filch are recognisable as the characters they would become. You interweaved canon, history and character so very well. And the end, that final twist of the canon knife (so to speak), is wonderful.