Sibylline Books

The Sibylline Books are a series of prophecies that we're used during ancient Rome due to the fact that they didn't use an Oracle. All of the prophecies effecting the Roman Empire were said to have been in these books, but it has been losted for centuries.

In, the Son of Neptune. the harpy, Ella seems to have discovered and read parts of the prophecies and briefly recited multiple lines from it.