Percy was halfway through an awkward attempt to get to his feet when a sort of invisible smoke hit him full in the face, and he collapsed as his head exploded with pain. It was the sort of pain that was nonsensical, like there wasn't really any possible physical explanation for it; surely there wasn't actually anything in actual real life that you could do that would hurt this much. As if every nerve in his body had been set on fire, all at the same time. That shouldn't be a real thing. For a moment he tried to reject it as impossible, it must be an illusion; but then that didn't actually help, and he gave up, because his brain simply didn't have enough processing power to ignore something so enormous.