The Great Rift was a terrible earthquake which was of such magnitude, it shook the very foundations of the continent of Corwyn and caused an enormous section of land south and west of the Cairn Mountains to sink beneath the sea.
When the earthquake took place in the year 884/3, it greatly enlarged the Sea of Ralas, created the Iron Sea, and created three massive, continent-sized islands: Renthara, Vesarivon, and Westvale. Both the gigantic Lake Miomar and the large Vale River, which divided the Eastvale and Westvale regions were consumed, and became part of the newly-formed Iron Sea.
Before that time, those 'islands' had been physically attached to the continent of Corwyn. The flooding caused by the Rift also created the gigantic marshlands region located south of the Reach; known today as the Saltmarsh.
Three different civilizations were devastated by the Rift.
- Wyntharë; an ancient nation of Grey-Elves was the hardest hit; its cities of Alarë and Wyn Falas were turned into rubble, and the elven city of Selunë disappeared beneath the waves forever.
- The dwarvish nation of Khûrzhad was devastated and its capital of Orthan Feyr also slipped beneath the waves.
- The human City-state of Asgamoth was consumed by the sea.