"So I took Neville into ritual ... hit him with a Celtic runic spell straight from the Potter dialect archives. It was a spell so powerful that it makes the Imperius Curse look like a gentle suggestion charm. I implanted the idea in his mind that there were weak crossing points to the international wards. Implanted it so deeply, so perfectly, that it would seem like a legitimate piece of his own world knowledge, just as if he'd read it in a textbook."