"Of course he does," said Luna breezily. "I imagine he already has a sacrifice in mind ... I mean, he's not short of enemies or people he wants revenge on. Any of them would do, and Harry is a useful sort ... he'd see the benefit of killing them to achieve his ends. Ironic, really, that he'll kill a bad guy to help with the killing of the big bad guy, isn't it? That will annoy whoever he chooses for it, so I imagine he'll choose carefully. Then it's just finding the right sort of stone."