Athas is the name of the fictional planet on which the campaign setting known as Dark Sun is set, for the Dungeons & Dragons fantasy role-playing game. It is a desert planet, due to the decay of its sun, and overuse of a form of magic (Defiling) which drains the planet's life force.
Athas was introduced in the original Dark Sun Boxed Set. The 1996 Dark Sun Campaign Setting, Expanded and Revised featured a portion of Athas eight times the size of that from the original set, and reflected the extraordinary political and physical changes that the world has gone through since its debut.
The devastation of Athas is the result of magic run amok. Most of Athas is an empty desert, interrupted by a handful of corrupt city states controlled by power-mad sorcerer-kings and their spell-wielding lackeys. Slavery is commonplace, gladiatorial duels provide entertainment for the elite, and treachery and death permeate the culture. As rain falls only once per decade in some areas, water is more precious than gold. Travelers risk dehydration from the scorching heat, ambushes from brutal elven raiders, and attacks from giant tentacles lurking in the dust-filled Sea of Silt.
Due to the scarcity of natural resources, few wizards have access to books made of paper pages and hard covers; instead, they record their spells with string patterns and complex knots. Metal is also rare, affecting both the economy and the quality of equipment. The ceramic coin, made from clay and glazed in various colors, is the primary medium of exchange, worth about a hundredth of a gold piece. Weapons typically consist of obsidian, bone, and wood, and are prone to break. Only a single dragon exists in all of Athas, a monstrosity with supra-genius intelligence whose appearance heralds disasters of catastrophic proportions.
Due to the harsh conditions of the planet, all the forms of flora and fauna have evolved to be extremely hardy and powerful as compared to the other races from other D&D worlds. Most, if not all, races on Athas have a unique self-defense mechanism that consists of psionic ability, enhanced strength, augmented agility, increased mass, lower food/water intake, superior visual/aural capabilities and/or various physical weapons.