The book is no ordinary volume; it is a linking book, which serves as a portal to the world it describes.
Atrus' grandmother, Anna ("Ti'ana"), helps Catherine by writing the Age of Myst as an escape route while Atrus destroys every other linking book on Riven.
A linking book to the Age of Myst, the setting of the original game, lies sealed in the ruins of the ancient D'ni civilization.
Players also receive a special linking book, a volume that serves as a portal to a personal world or Age, known as Relto.
The Stranger's discovery of the Myst linking book saves Atrus from being trapped in K'veer a second time, and Catherine from Gehn's clutches.
When Saavedro is unexpectedly freed and travels to Tomahna in hope of finding the brothers, he steals the linking book for Releeshahn in a plan to lure Atrus to Narayan and exact revenge.
The linking book to Myst is dropped into a starry expanse known as the Star Fissure, where it is presumed lost (but later found by the Stranger, beginning the events of Myst).
Ti'ana raises Gehn until he runs away as a teenager, learning the D'ni Art of writing linking books.
The player is summoned by Atrus, a man who creates links to other worlds known as Ages by writing special linking books.
