Dark Sun: Gulg
Arcane Magic manifests in many forms on Athas, each of them reviled. The reason is that Arcane magics draw in the energy of life, mostly commonly in the form of plants and nutrients in the ground.
When drawing the energy for a spell, any Arcanist can choose to defile or preserve the land. A person who defiles pulls as much energy as possible as quickly as possible into the spell to power it, and the source of the energy is harmed or destroyed. To preserve, an Arcanist pulls the precise amount of energy needed for the spell, and does so cautiously. With minimal practice, preserving takes the same amount of time as defiling.
Defiled land loses nutrients needed to grow plants, and plants turn to ash. Defiling often leaves area cursed in strange ways, warping creatures into aberrant abominations. Defiling can also harm people the arcanist considers allies.
Defiling can also reduce material components needed for casting Arcane rituals. It is also addictive, and Arcanists who defile feel a rush of obscene pleasure.
Most Athasians don’t know the difference between these two forms of arcane use.