The Thar Desert covers a significant arc along the dawnward third of The Whorl, touching on one edge of the Dawn Sea and extending down one side of the Great River, abutting Videha, before eventually giving way to scrubland, and eventually the Dundaka Forest.
Although the dawnward third of the Whorl has always been hot and dry, there was no desert until the Godswar, when the greatest battles at the end of the war were fought on the soil of the Eternal Solar Empire. Ayodhya's armies met with the regiments of Dragonborn and the other combined forces of the gods where blood spilled on the sands, and Surya's desperation caused the sun to burn brightly in order to scorch his enemies and deprive them of water. After Surya's downfall and imprisonment, the former scrub plains and savannahs where the battles were fought never recovered.
The Thar desert is an expanse of hostile sand and rock where the wind reshapes geography and its easy to become lost and disoriented among the arroyos and dunes. Still, there are entire communities of nomads who live here, moving from the hidden oasis to oasis, trading with each other and those more settled communities at the edges of the desert. It is rumored in those bastions of Civilization that the nomadic tribesmen have uncovered mighty magics and machines of war from beneath the sands. It is true that their shamans and sorcerers engage in practices that seem alien to most observers.
Sarya: The ruins of the ancient city of Sarya sit near the center of the Thar Desert providing a location of nominal shelter that has, over the years, become a place of gathering and trade. Nomadic tribals, mystics, warriors of the Kreen, and agents of Ayodhya and Videha all mix alongside other, esoteric peoples to barter or rest between legs of their desert voyages. All manner of exotic goods can be found here provided you know where to look and who to ask. Even slaves are sold, usually to agents of Ayodhya where the practice is still legal. The city is literally named after the fallen god Surya, albeit in an archaic dialect no longer spoken. Historians note that Sarya was once the largest city in the Eternal Solar Empire, eclipsing its capitol Ayodhya itself. Now it is merely a sand-blasted, sun-baked collection of tumbled stones.
The Three Hives of the Kreen: The Kreen, insectoid humanoids who live exclusively in the Thar Desert, have always organized themselves into three "hives." Indeed, those who have studied their odd pheromone-augmented language conclude that "kreen" is a word meaning both "people" and "hive," making the phrase "thri-kreen" literally mean "three hives." Nobody knows how the Kreen came to be. Historians note that they appear in records from the last days of the Godswar, arising in the blasted, war-torn wastes that were to become the Thar Desert, fighting against the forces of Surya. The prevailing theory is that they were created by Parvati to tend to the ravaged land and slowly restore it. The Queens pass on perfect eidetic memory to their daughters, ensuring that each of the Three Queens has centuries of accumulated wisdom. Some note that this is a clever way around the gods' ban on immortality.