A wizard is able to capture and master magical energies. On Athas, magic and the ecosystem are irrevocably bound —no one, not even a wizard, can affect one without affecting the other.
All wizards must decide at the beginning of their careers whether they are trying to work with nature or without regard for it. In Dark Sun, if they decide to work without regard for it means the wizard must be a Defiler.
The defiler is a wizard who activates tremendous magical energy without regard to its effect on the environment. With the casting of each spell, a defiler destroys a portion of the world's ecosystem, rendering it dead and sterile. The means by which a defiler learns and uses magic is comparatively easy to master, so he advances quickly. A defiler can be either a noble, freeman, or slave.
Arcane powers are hazardous on Athas.
Defilers leech energy from the land, stealing life away with every spell they cast and leaving only dead ash behind. Defilers are mortal enemies of Preservers, stand locked in a never-ending battle -with the survival of Athas at stake.
Reviled and hunted, hated and feared, Defilers live in secrecy, hiding who and what they are from the rest of the world. They are criminals whose crime calls for swift execution. They are oucasts, with no place to call home. They are Wizards, and their crime is the practice of magic...
Beneath the crimson sun, the life of a Wizard is hard and dangerous. Blamed for the conditions of the world, feared for the mysterious power they wield, and hated for crimes both real and imagined, Athasian Wizards walk in the shadows of civilization and in the barren wastes of the wilderness. For to reveal their nature is to admit their crime —and risk their very lives.
Long ago, no one knows for certain except maybe the Sorcerer-Kings and Rajaat, Athas bore a defect. This defect allowed for powerful magic, enough to destroy kingdoms and raise armies out of nothing. However, those who used such power were doomed to blight the land.
The greatest example of the blight are the Deadlands, created by the Defiler Qwith, under tutalige of Rajaat. She was able to open a gate into the Inner Planes, which spouted a sea of Obsidian.
While Defiling Magic is not culturally acceptable, most Defilers have to seek out power on their own, except Sorcerer-Kings, though they would gladly see a Defiler die rather than master the art.
Magic used by Defilers is gathered from plant life. Using too much kills the plant and defiles the soil so nothing will grow.
Those who master Defiling Magic are able to shed their original form and become Dragons. Currently there has only ever been one dragon, Borys, though almost every Sorcerer-King hopes to reach full dragon-hood.
- Dark Sun Boxed Set. 2nd Edition. TSR Inc.