"Well, under the terms of the prophecy, Riddle could kill me," Harry explained. "We are linked by that. I looked into a lot of rituals that might somehow break that link, but he'd cursed me already. My scar, you see, it's full of a sort of poison that came with the curse. As long as Riddle lives, it renews and refreshes itself along that magical link between him and me ... and it's spreading."