User blog comment:Menara/The Son of Sobek: The official PJ and Kane Chronicles Crossover/@comment-90.149.162.73-20130507161935/@comment-3146930-20130508015411

I actually have to side with the Anon on this one. The first time Percy heard of them was during the Prophecy of Seven, but no one really knew what they were. Percy only got an idea after Mars and Nico mention it at the start of The Son of Neptune. As far as Thanatos letting people go, I don't think he does it that often as he even told Hazel he would most likely take her back to the Underworld even if she saved him, but only let her go as she wasn't on the list. But that means that this book can only take place after the HoO series, which is kind of like a big Ha Ha Ha by Rick, as he is telling us everything turns out fine.