The Heirs of Nithera and Ōkeanos

The planet Ōkeanos has met its end. Earthquakes are breaking grounds and homes. The sun is boiling up the waters in certain places. Percy and Annabeth are the only survivors as their parents sent them off in an escape pod. They land in Nithera, a planet of earthen shadows ruled by King Hades who, years later, wishes to associate his kids with the rare species. Nicercy alien!AU