Dragonlance: Dragons of Eternity

An intrepid woman and her friends must somehow undo the great damage they have done to the future of their world in the thrilling conclusion to the New York Times bestselling Dragonlance series
When Destina Rosethorn and her companions were transported to a time 300 years before their birth-to the days of the Third Dragon War famed in song and story-the last thing they wanted to do was upset history. But upon returning to the near-past from which they departed, they discover a world completely altered.
Thanks in no small part to the Graygem of Gargath that Destina carries, the war that was once won is now lost, and the forces of evil hold sway over the land.
The river of Time is rising, flowing inexorably towards present day. So it is up to Destina and her friends to make one last, desperate attempt to restore Time's river to its proper channel. For if they cannot manage it, the altered past will sweep over the present until no trace of their old world remains.