The Cataclysm (Great Destruction) was a catastrophic event that occurred when the Kingpriest of Istar demanded to be given godlike powers in order to eliminate evil from the world. The gods threw down a fiery mountain upon the Kingpriest and all of Istar for his impunity. The result of this destruction was the creation of the Blood Sea of Istar.
Along with the loss of Istar, the rest of the continent was shattered by quakes and disease came with great pestilence. Perhaps the most tragic of all was that the gods of light receded, leaving the mortals to fend for themselves.