An interesting start but please do not make Harry so overwhelmingly powerful that he can defeat any order member in a duel. Just because he has the knowledge doesn't mean he can use it well (yet).
As for the ship, I don't mind Harry/multi but just don't overdo it (we don't need a new girl every chapter, no one is able to resist him, etc).
This is well written apart from a few odd phrases here and there. There is potential here and I can't wait to see what you do with it.