[Heeeeeeeeeeeeeeellllllllllllllll no he's not saying anything about the Achilles "heel." The only one who knows where that is is Annabeth. And he's worried because that's really the easiest part to guess, at least in that he has one now, for anyone familiar with myth.]

Hey, it was your idea, you know. But I'm not gonna tell them anything - I don't think Egyptians or Norse can get to our Underworld so they wouldn't matter, but no one needs to go Styx-swimming again.

[He unconsciously shudders at that memory. That was the least pleasant thing he's ever done.]