The House of hades
The House of Hades – At the end of The Mark of Athena, Annabeth and Percy had fallen into a pit leading directly to Tartarus. The remaining five demigods had to suppress their grief, follow Percy’s instructions to find the way to Cua Tu. If they could fight Gae’s army, Percy and Annabeth could survive at the House of God Hades, the seven demigods could seal the Death Gate from both sides and stop the relay of Gae for the giants. But Leo was concerned that if he closed Door Tu, how would Percy and Annabeth get out?