Tocasia, along with her students, brothers Urza and Mishra made an archaeological trip to the Caves of Koilos where they found two complementary ancient Thran artifacts - a Mightstone and a Weakstone. As the excavation continued, the brothers eventually engaged in combat; in an attempt to calm the situation, Tocasia was killed by the power of the two stones. Urza and Mishra, furious with each, went their separate ways. This event would serve as the catalyst for the Brothers' War - a decades long conflict which left wounds on Dominaria that are still felt thousands of years later.