But it doesn't even have to be anything super powerful, this ritual. Imagine if it really defeated Death with the capital D - people would be keen on it, wouldn't they? Maybe it is something relatively mundane, like Comed Tea. You perform it and it automatically guides you to the nearest fatal trouble. Ideal for a HPMoR version of a Triwizard Tournament, with the prize being learning the anti-spell. I mean, it certainly seems like it will be an important thing, but that doesn't mean we can privilege the hypothesis that it will be THE way Harry will win.