Elvish curse

Ancient magic, lost to modern beings, the Elves once used a great curse to level their homeland forests and turn the entire land into a white ash. The region is now known as the Eternal Desert. This curse corrupts life. The elves' forest, created and interwoven with purity, could not be corrupted and was destroyed by this attempt. the many sapient individuals inside the expansive forest were likewise destroyed.

Effect

Reduced life to its worst state, i.e. sapient life become evil, good plants become poisonous, tame beasts become viscous predators. It is believed that the orc are the remnants of King Marothsa's army which were corrupted by the curse.

Side/Secondary Effects

Magically pure life, such as the trees of the great forest, are destroyed by the curse, and reduced to white ash, commonly mistaken for sand. Pure life, humans or elves, should also be destroyed.

Manifestation

A black fog envelopes the area or creature. It is impossible to dispell, except over small areas, or without resistance. Exactly seven hours later, the creature experiences great pain and is agonizingly killed or transformed.

Source

Ancient elvish magic, unknown in origin. Thought to be a product (somehow) of the guardians.