User blog comment:Hyperborean/"The House of Hades" – official expectations blog/@comment-15860919-20130920200144

I have a theory, in The Titan's Curse, Athena reveals that Percy's fatal flaw is personel loyalty, so what if Percy stays in Tartarus, lets Annabeth go through before the Doors Of Death are sealed, and seals it and stays in Tartarus, also, you don't suppose that Luke may visit Tartarus from wherever he's staying in the underworld and help Percy and Annabeth, or Piper could just charm speak a monster to seal the doors from Tartarus so Percy and Annabeth dont have to stay in Tartarus