They are really quite wonderful if you give them a chance, but I'm totally respectful of your choices. That fandom is scary, and aside from some RPing back in the day, I haven't ventured into it at all.

Patronuses are protection spells cast to scare away dementors, which are sort of like... I'm trying to think... Well, they make you think of the worst memory you've ever had and you relive it until you're paralyzed. They also suck out your soul through your mouth, in extreme cases.. So you cast a patronus, by thinking of your best memory and it takes the form an animal, and the animal chases away the dementors. I'm not sure if you knew that, but it's most obscure thing there.

I can so picture Harry getting himself into trouble by casting a transformation spell he can't undo. I kind of picture half of Harry's life is him sitting bewildered, wondering what the hell just happened.