The game takes place in the fictional land of Athas, a dying and hostile desert world. The locale is Draj, a city-state ruled by a powerful sorcerer-king. Nearby are several "free cities", surviving in the desert thanks to the hard work of their citizens. Upon the completion of the pyramid in Draj, the Sorceror-King desires to make a great sacrifice of blood by sweeping the desert and destroying the inhabitants of the cities not under his control. The player controls a party of up to four gladiators, condemned to fight in Draj's arena until they die, so naturally the first order of business is escape. Upon escape, the party must unite the free cities to resist Draj's army.
Source: Wikipedia, "Dark Sun: Shattered Lands," available under the CC-BY-SA License.