"Voldemort tried to kill you when you were a child because of a prophecy made shortly before your birth. He knew the prophecy had been made, though he did not know its full contents. He set out to kill you when you were still a baby, believing he was fulfilling the terms of the prophecy. He discovered, to his cost, that he was mistaken, when the curse intended to kill you backfired. And so, since his return to his body, and particularly since your extraordinary escape from him last year, he has been determined to hear that prophecy in its entirety. This is the weapon he has been seeking so assiduously since his return: the knowledge of how to destroy you"