Defilement

The Price of Magic

Beneath the burning orb of the Dark Sun, magic is inherently tied to the flora and fauna of Athas. Energy for spells and magical effects is drawn from living things (usually the land and plants). Decimated by centuries of irresponsible magical manipulation associated with this drawing of living energy, Athas struggles to survive. Some few—those who call themselves preservers—fight to restore the land, to save it before all is lost. Theirs is an uphill battle. Pitted against them are the remaining sorcerer-kings and other defilers, those who leech the life from the plants and the very soil to power their spells without giving anything in return. Defilers have turned the once verdant forests and plains of Athas into a wasteland. Their predations have left tracts of barren ground lifeless and scarred.

Defiling

Every spell cast on Athas has the potential to defile the world, and only a select few can restore it. Other magical effects besides spells also have a similar defiling effect. Though society hates defilers, sometimes it may be necessary to draw the power from the very earth in order to survive. Still, even a small defilement is considered enough to condemn a mage to death. Outlined below are the rules for defilement as used by PCs and NPCs. Preservation magic is any magic that doesn't use defilement.
For all types of defilement, the terrain around the defiler is most important. It can be classified into 4 categories, each with a point value associated with the amount of vegetation. You may use some or all of the points in the area, which may reduce it to a category of lower value that can be used later. In general, you can defile as long as part of the vegetation is within 60ft. The area affected by defilemnt depends, but is typically a 30ft. radius from the point the energy is drawn from. The following are the four categories:
0 - No plant life in the area. Defilement is not possible.
1 - Patches of grass and/or small cacti.
2 - Grassy field or lots of vegetables and fruit.
3 - Dense vegetation.
Regardless of the result of defilement, you gain defiler points equal to the amount of land defiled. These points are cumulative and manifest as an aura in the presence of certain magic. You must roll a d100 whenever you defile. If the number rolled is less than your defiler points, you take necrotic damage equal to your defiler points and your maximum hit points are reduced by the same amount. This reduction lasts until your defiler points reach 0. If this reduces your maximum hit points to 0, you are transformed into a t'liz. You may reduce your defiler points each time you complete a long rest near vegetation; the amount is equal to the level of vegetation. A Lesser Restoration or Remove Curse reduces a creature's defiler score by 1, a Greater Restoration reduces a defiler score by 5, and the Heal spell reduces it to 0. 

Spellcasting

The most common form of defilement is that done by mages and wielders of the arcane.
You may choose to defile in the following ways:

• You bolster the power of your spell. When you cast a spell that can be cast at higher levels, the spell slot may be counted as a higher-level slot. The level equals the original spell slot plus the points for defiled land. For example, a 1st level guiding bolt in dense vegetation using the maximum amount of defilement would be counted as a 4th level guiding bolt.
• You attempt to siphon the power of the spell off the land. As an action, or when you cast a spell using a spell slot, roll a d20, adding your spellcasting modifier and twice the points for the amount of land defiled. The DC is equal to 10 + the level of the spell. On a success, you regain the expended spell slot.

Hemocraft

Though masters of siphoning their own life force for power, hemocraft experts may also pull on life from the world of Athas in order to defile.
You may choose to defile in the following ways:

• You pull the life from the land into your blood. As an action, or when you use your Blood Maledict feature, roll a d20 and add your hemocraft modifier and twice the points for the amount of land defiled. The DC is equal to 14. On a success, you regain one use of your Blood Maledict.
• When you activate your Crimson Rite or amplify a blood curse, you may choose to forgo the role of your hemocraft die.

Ki

Their stoic reputation belies the nature of ki-based defilement, a powerful and useful tool.
You may choose to defile in the following ways:

• As an action, you can pull on the land to regain Ki points equal to the land defiled.
• When you use a monk ability that requires a saving throw, you may defile to increase the DC of that saving throw by an amount equal to the land defiled.