The Book of Eternity has been entrusted to the care of Zeus, Poseidon, and Hades. They are responsible for safeguarding the book's contents and keeping the power of Cronos, which is contained inside it, from falling into the wrong hands. They do this by assuming human form and blending in with society, constantly reinventing themselves by switching identities, jobs, and houses.
Zeus loved the high life of the prosperous and famous. He portrayed everyone from mighty rulers to prosperous businesspeople throughout history. He took great pride in his newfound authority and used it to keep a watchful eye on the quest for the Book of Eternity.
Conversely, Poseidon relished his life as a strategic advisor to the powerful. He acted as a political advisor and a military general, utilizing his wit and intelligence to steer the powerful in the right direction and away from the Book of Eternity.
Hades, king of the underworld, was the wild card of all the guardians. He was a prosperous businessman, a vicious mob boss, and a respected academic. He was perpetually morphing into whatever form would serve to keep the Book of Eternity's secrets safest.
These three protectors took vastly diverse ways to existence among humans, but they have one in common: they were immortal. They survived for thousands of years, maintaining vigil over humanity and making sure the Book of Eternity was never compromised. Over the years, they perfected the art of hiding in plain sight, hiding among regular people without being noticed.
The protectors' ultimate objective was to keep Cronos, the villainous king of the Titans, imprisoned in the Book of Eternity. They kept a sharp eye out for trouble and quickly responded to any threats they saw. No matter what it took, they were going to keep the Book of Eternity's secrets safe.