The Empire of Istar was once considered a shining example of all that was good in the world. Located in the eastern half of Ansalon, it first grew to prominence in the years of peace that followed Huma banishing Takhsis.
But Istar rotted from within. Originally ruled by a Council of Elders for hundreds of years, the Kingpriest of Istar, through careful machinations, wrested political control in the decades prior to the Cataclysm as part of his effort to purge evil from the world. He instituted a theocracy, with himself at the head of the government.
Then came the Cataclysm, as the Gods hurled a fiery mountain upon the Kingpriest as he demanded their power. The region was shattered, and the seas rushed in. Where the Empire of Istar once was, the Blood Sea of Istar now is.