Madrius Dark Sun
The system for casting magic on Athas is one that draws from a life force, or mana. Various people can tap into the metaphysical realm of mana. Wizards have learned incantations and rituals to harness it, and sorcerers (those with a Sorcerer-King or Queen in their lineage) have an innate ability to shape it at will. It takes no form that the five senses can detect. Mana is simply the life force within all plants and animals. The more mana the more life in an area. To drain all the mana in an area would kill or injure the living things in that area. There are two commonly practiced ways of drawing from this mana.
Defiling is quick, easy, and exhilarating. However, it comes at a cost. There are many visual clues as to when someone is defiling. Plants wither to ash, animals feel sudden and intense pain. Be cause defiling draws from the immediate surroundings the magic associated with it can be more powerful. Rampant use of defiling is what turned Atahs from a lush green planet to a harsh desert planet.
Unlike defiling, preserving is slower and requires more discipline. A preserver can tap into the mana stream and draw tiny bits from all over Athas. By doing so, no harm is caused and the planet can easily recover from it’s loss. One must be taught to preserve, or spend years meditating to come to the process on their own.