Rick Riordan : The Blood of Olympus

Seven heroic demigods. One final quest. The greatest sacrifice yet. 'The ruins are up there,' Piper promised. 'I saw them in Katoptris's blade. And you heard what Hazel said. 'The biggest' - ' ''The biggest gathering of evil spirits I've ever sensed.'' Jason recalled. 'Yeah, sounds awesome.' After battling through the underground temple of Hades, the last thing Jason wanted was to deal with more evil spirits. But the fate of the quest was at stake. The crew of the Argo IIhas a big decision to make. If they chose wrong, they would fail, and the entire world would be destroyed . . .