These ancient Documents are known as the Gaia Manuscripts. They tell the legend of a disaster that befell our planet some tens of thousands of years ago. — Professor Pickle, Sonic Unleashed
The Gaia Manuscripts (ガイア文書,Gaia Bunsho?, lit. "Gaia Documents") is an object that appears in Sonic Unleashed. These manuscripts are an ancient collection of documents, records and knowledge chronicling the time of awakening that occurred tens of thousands of years ago. They were initially stolen by Dr. Eggman in his attempt to awaken Dark Gaia, but they were reclaimed by Sonic and his friends who used them to undo the doctor's work.
The Gaia Manuscripts contains an encyclopedia of knowledge concerning everything connected to the disaster created by the second-most recent time of awakening, such as records of the disaster, info on the Gaia Temples and their locations, the nature and weaknesses of Dark Gaia's Minions, a detailed description of Dark Gaia and its being, and scenarios of what would happen should Dark Gaia succeeded in its mission. These texts are written in an ancient language that so far only Professor Pickle has been able to decipher.
Some tens of thousands of years ago, the time of awakening occurred, where the earth was split into pieces by Dark Gaia, only to be returned to normal by Light Gaia. At some point either during or after this cataclysm, the Gaia Manuscripts were created, chronicling the event and documenting the info that had been gained.
In the present day, the Gaia Manuscripts came into the possession of Professor Pickle, an expert on ancient literature
In Sonic Unleashed, the Gaia Manuscripts were stolen by Dr. Eggman. After acquiring the knowledge in the Gaia Manuscripts, Dr. Eggman devised his Chaos Energy Cannon to awaken Dark Gaia so he could harness its power for his own use. The Gaia Manuscripts were then stored inside a vault in Eggman's base in Mazuri, where he kept Professor Pickle captive as well.
When Professor Pickle was freed by Sonic the Werehog, Tails and Chip, after Dark Gaia had been awoken, the group reclaimed the Gaia Manuscripts. With the manuscripts, Professor Pickle formulated a plan of action for Sonic, enlisting him to seek out the Gaia Temples in the manuscripts which could restore the planet from its shattering. The Gaia Manuscripts remained in the professor's care from there, who kept researching them for additional information, such the location of the Gaia Temples and the means for Sonic and Chip to free people from the influence of Dark Gaia's Minions.
"The abomination grows strong on the negative energies of the world, sleeping within its core for millennia in wait..."
—Gaia Manuscripts, 4:11.
"When the beast is complete, its dark arms shall encompass the planet, ushering in the end of times. The world, in death, will fall into a deep sleep in waiting for the time of rebirth to come."
—Gaia Manuscripts, 4:28.
"And the world shall be plunged into the dark of night, the dark of destruction."