User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-9703010-20130920114519

Is Cocytus the river on the cover? If so, it would make sense because 'Annabeth was still shivering from the chill of the River Cocytus' The river on the cover is blue. And 1 more thing: Cocytus and Phlegethon are in the underworld but not in Tartarus. So HOW does Rick speak about the Tartarus when Percabeth isn't in Tartarus?