User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-5604127-20130302213549/@comment-2079715-20130303201204

Since there wont be any Percy's or Annabeth's POVs, it leaves only Coach Hedge and Nico as the 4th POV. And since Coach Hedge is only a support character, Nico is the only logical choice for POV. I think Nico will play very important role in The House of Hades.