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.