Once Zeus, Poseidon, and Hades sealed Cronos and his power in the Book of Eternity, they realized they had to do everything it took to keep the book out of enemy hands. In the event the book was discovered, its power would be too great for any human or immortal to withstand, and it would be too dangerous to leave in the hands of just one person.
The Olympians chose to take in human form and blend in with the populace, regularly switching jobs, homes, and other details to avoid detection. They moved around to different areas, used false names, and generally tried to stay out of trouble. Hades lived the life of an entrepreneur, a ruthless mafia godfather, and a university professor, while Zeus enjoyed the life of a powerful and respected figurehead, Poseidon enjoyed the life of a strategic thinker who advised powerful people and organizations, and Zeus enjoyed the life of a successful and well-respected person of prestige.
For added security against the immortals who sought to free Cronos, they conjured up enchanted devices known as the EternalProject to keep track of the trustworthy individuals who had been entrusted with the book's care. Furthermore, the EternalProject assisted in hiding their identities as the book's guardians.
The Olympians were similarly cautious about concealing the whereabouts of the book, sharing it only with a select group of individuals and then only when absolutely essential.
The Olympians devised a language that only they could understand, allowing them to discuss the book's whereabouts and other sensitive matters among themselves without fear of outside interference.
To further complicate matters, the Olympians had cast potent charms and enchantments surrounding the book's location. These magical protections were put in place to make it nearly impossible to locate the book by disorienting and confusing anyone who came near it.