The World Of Tysis
The Sundering is a little understood event of ancient history.
During the end of the Demongate Wars, when the Demon Queen and her Five Children walked the word of Kasan, the gods stepped in to save the world, this one and only time. They were vulnerable on the surface, and some perished in battle, but they were able to seal the Five Children within the earth itself, and banish the Demon Queen to a prison outside of time. However, as she was being sealed away, with one last act of defiance and power she reached out and smote the world, shattering the single land it was, and sending the separate islands sailing their way across the ocean floors. the devastation to many of the regions was complete, and it is said that only a tenth of the population of the planet survived.
To this day, the great islands of the world grind across the ocean floors, inevitably heading into collisions and contact as they grow closer together.