The Book of Translation is an artifact in the possession of the Ogier. Its full capabilities and origin are unknown at this time. However, it is known that the Book possesses the power to move or transport the Ogier race between worlds. Whether this is between different planets or different reflections of this world (such as the portal stone dimensions) is unclear.
The Ogier used the Book of Translation to come to this world some immeasurable time before the War of the Shadow, during or before the Age of Legends, and according to prophecy or history they believe they will one day use the Book to depart this world. According to the Ogier, there are some Ages of the Wheel of Time in which they are not present in the world, and during these times they exist somewhere else. When the appropriate Age comes again, they will return via the Book of Translation.
The Ogier have always had the option of using the Book of Translation to flee should they ever be imperiled as a species, yet chose not to exercise this option during the War of the Shadow, nor even during the Breaking of the World that followed it. They also chose not to flee during the Trolloc Wars. In each case they stood and fought the Shadow alongside their human allies. However, in 999 and 1000 NE the Ogier Great Stump began meeting to discuss opening the Book of Translation and fleeing ahead of the Last Battle, which, it was becoming increasingly clear, was imminent. The Ogier fell into two camps during the argument, one favoring this move and the other opposing it, on the grounds that should the Dark One win the Last Battle, then any other world they fled to may be in danger as well. There was also the matter of Longing, which may result in the Ogier dying if they are moved from the proximity of the stedding for more than a few years. Covril of Stedding Shangtai was not in favor of opening the book, but spoke for doing so anyway in order to give a strong argument for both sides. Elder Haman and Covril's son Loial take the opposing view, and Loial's speech eventually convinces the stump that the Ogier should remain and take part in the Last Battle.