Sibylline Books

The Sibylline Books are a collection of prophecies that were used during ancient Rome. Only fragments have survived, the rest being lost or deliberately destroyed.

History
Passed down from an Oracle called the Sibyl of Cumae (not to be confused with a fertility goddess Cybele). All of the prophecies effecting the Roman Empire were said to have been in these books, but they have been lost for centuries.

The Son of Neptune
In, the Son of Neptune, the harpy Ella seems to have discovered and read parts of the prophecies, as she briefly recited multiple lines from them. The prophecies relate to the fates of Rome and to Camp Jupiter. Octavian wants the books desperately, as he feels he could use the prophecies to control the camp and become the next Praetor. Percy and his friends agree to hide Ella from him so he can't use her knowledge.

Trivia

 * It is hinted that Ella probably has memorized parts of the Sibylline Books as she also recites prophecies.