User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-5850470-20121217235414/@comment-5851009-20121218155230

First off, I think the whole book will only be about their journey to the Doors of Death (even possibly just the Argo II's journey) and a battle between Camp Jupiter and Camp Half Blood. The climax might be them finally arriving at the House of Hades and finally lifting Athena's curse and saving both camps somehow. However i think the line "An oath to keep with a final breath" will lead to Nico dying on the way to bringing them to the doors of death.

The last book might focus on Annabeth and Precy journey thru Tartarus and the final battle on both sides of the doors which will probably include all the demigods from both camps .I think, the climax will feature Jason or Leo having to die to save the world ("''To storm or fire, the world must fall."). People have been speculating that this means either of the 2 will be the cause of the world's downfall, but it may mean the task of saving the world must fall to either storm or fire'' (a stretch i know).

Its also been mentioned twice (by Phineas, and by Mars) that Percy will be faced with making a sacrifice that he will not have the courage to make. I think Percy will have the chance to save one of them but won't be able to make that decision and Frank will be the one to make the hard choice for Percy and quite possibly have to sacrifice himself as well. Alternatively, Annabeth might have to be the one to help Jason or Leo sacrifice themselves to save the world but Percy cant let her go, so Frank will be the one to take Annabeth's place.