ruler of Riven. Thirty years earlier, Atrus and Catherine trapped Gehn on Riven by removing all of the linking books that led out of the Age; the last book to be removed, linking to the Age of Myst, was the one they held to escape Riven. In the belief that it would be destroyed, they let the book fall into the Star Fissure, a rift leading out of the damaged Age of Riven into a mysterious, space-like void. Catherine was later tricked into returning to Riven by her sons, Sirrus and Achenar, whereupon she was taken hostage by Gehn. Eventually, the player discovered the unharmed Myst book, leading to the events in Myst. At the beginning of Riven, Atrus equips the player with a trap book—a snare that functions as a one-man prison, yet looks identical to a linking book—and his personal diary. This diary summarizes the history of events leading to the present situation; Atrus cannot explain in depth as he is engaged in rewriting the descriptive book of Riven, in an attempt to slow its deterioration. The player must enter the Age with no way of leaving, as Atrus cannot risk sending a real linking book to Riven until Gehn is safely imprisoned lest he use it to escape Riven. Instructing the player to capture Gehn in the trap book, find Catherine, and then signal him, Atrus holds out the link book that will transport the player to Riven. Once there, the player explores the islands of Riven, eventually discovering Catherine's prison. The player also travels to Tay, the Age of the Moiety (rebellious Rivenese under the leadership of Catherine who are attempting to end Gehn's tyrannical rule), and the "233rd Age", Gehn's personal sanctuary, where the player meets Gehn himself. Gehn attempts to convince the player that his intentions to rebuild D'ni (the civilization responsible for originating the art of the link books) were honorable and that he seeks atonement for his past transgressions. Because of the decay of Riven's structure, the only way to clearly signal Atrus is to bring about a massive disturbance in the Age's stability—accomplished by reopening the Star Fissure, which Gehn had closed. When it opens, Atrus immediately links to Riven to investigate and meets the player at the brink of the Fissure. Depending on the player's actions, the ending to Riven varies. In the best ending, the player tricks Gehn into