Perserver/Defiler
By Ed Piper
All wizards of Athas start with the power and choice to defile or not to defile. Unfortunately the more often a wizard takes the easy, more powerful route of defiling, the more likely the wizard is to give up his ethics and morals. In the simplest terms a preserver may choose to defile, but he runs the risk of becoming a defiler. A defiler can only defile.
Additional spells
By using defiling magic, a wizard may cast more spells than he would normally be able to cast. When memorizing spells a preserver can memorize a bonus number of spells equal to being 2 levels higher on the chart as defiling spells (i.e. a 3rd level wizard could memorize an additional 1st, and additional 2nd and an additional 3rd level spell)  There is no consequence for memorizing these spells, as long as they are not cast. Bonus spells of a level not known can be used to memorize metamagic spells of a lower level. Each time that one of these defile spells is cast, the wizard may permanently change to a defiler, if he is not one already. (See Consequences)
Increased spell effects
A wizard can gather more spell energy by defiling than he can with preserving techniques. If a preserver chooses to defile, he can cast any spell that he currently has memorized as if he were 2 levels higher than the level he actually is. The higher casting level applies to all aspects of a spell’s performance-range, duration, area of effect, or damage-normally affected by the caster’s level. With this effect, a 5th- level preserver could cast a 7-die fireball with the increased range of a 7th-level caster. (See Consequences)
Consequences
Each time that a mage defiles he has a chance of no longer having a choice between defiling and not defiling. Each use of the defiling he must make a Willpower save with a DC of 10+ level of spell +1 per incident or lose the ability to cast spells as a preserver. A preserver needs to keep track of the number of incidents in which he has defiled in order to know the correct DC. Eventually a preserver who constantly defiles will have a DC that he cannot roll, with the exception of a natural 20. 
A player who uses a defile-memorized spell with increased spell effect is considered to be one incident, and only one save is required.
Effects of defiling
Defiling causes an Area of Destruction dependent the type of terrain. The less foliage, the greater the Area of Destruction, as the draining tendrils of defiler stretches out over the land gathering energy. Use the chart below to figure out the radius of the Area of Destruction.
All sentient plant life take 1 hp damage/level of the spell.
All other life forms, except undead and constructs take a initiative penalty equal to the level of the spell.
Balancing the Defiler
Once a player has become a defiler he can use the additional spells and increased spell effects without fear of change. It is now up to the DM to balance the game. Remember that everyone hates defiles(except certain para elemental clerics). Dragon Kings fear that they will grow in power, clerics and druids see them as a plague, and the veiled alliance constantly hunt them. Make sure your players know power has a price.

*This set of rules is based on an article originally published in Dragon *