The Exemplar Crass (Book of Tomorrows) was a book written in the 16th century by an Italian Duke. Its pages alternated between black sheets with white printing, and white sheets with red printing. The book contained uncannily accurate predictions of future events, as well as warnings of an apocalyptic event due to hit just before the end of the millennium, when the aliens would return.
After the defeat of the Brotherhood of Demnos, Duke Giuliano organised the survivors into a beneficent group known as the Orbus Postramo (Orphans of the Future). His journal describing his adventures with the Fourth Doctor and Sarah Jane Smith became the Book of Tomorrows, and the cult took it as their sacred text. Over time the group broke into two factions, the White Chapter and the Crimson Chapter, with each attempting to claim their respective pages of the Book. Many of the pages were lost entirely. Because Sarah Jane was described in the book by Giuliano, the leaders of both factions in the 21st century believed her to be the herald that would precede the End of Times. (AUDIO: Fatal Consequences)