The Widow Harun
Ancient Imaskar was a human empire that dominated the area of modern day Raurin as well as much of The Eastern Realms and The Endless Waste many thousands of years ago. At their height the Imaskari were in competition with Shou Lung for the areas that now form the eastern border of The Tuigan Empire. Imaskar was destroyed by rebellious slaves from the Mulan ethnic group, whom the Imaskari had imported from an alternate dimension via enormous portals. The death of Imaskar left a vast number of ruins and tremendous desolation in the form of the twin deserts of Raurin.
Imaskar is described in much more detail in the Forgotten Realms core books and supplements. Please consult these if you wish to learn more.