Though Rachel is the only Pythia or priestess among the Oracles, the other Oracles are unique in their own way. One is the Sibyl of Cumae, who wrote the Sibylline books, prophecies memorized by Camp Half-Blood’s resident harpy Ella. The demigods at Camp Jupiter are now trying to reconstruct the prophecies based on Ella’s recollections. There are also the Oracles of Erythaea and the Cave of Trophonius. The oldest is of course, the Grove of Dodona, planted by Rhea, the Mother Goddess who preceded Gaia and gave rise to the first generation of Olympian gods. Apollo believes the crowned woman whom he has been seeing in his dreams is Rhea, a beneficent goddess who fought for the gods in their first great war. However, Rhea has not been seen for thousands of years since her grove was burned by the cruel ruler Theodosius in ancient times. Though the grove was incarcerated, if the Labyrinth can rebuild itself in modern times, so can Dodona.

In the old days, the energy of the trees of Dodona was focused by caretaking priests and priestesses. With the priests gone, the voices of the trees are unfocused, driving mortals to madness and luring them into the woods, where they are captured by a waiting malevolent force.