Sandmagic
Word spread through the tribes of the Abadapnur that a would-be sandmage was loose in the desert, and all were ready to kill him if he came. But he did not come.
For he knew now how to serve the desert, and how to make the desert serve him. For the desert loved death, and hated grasses and trees and water and the things of life.
So in service of the sand Cer went to the edge of the land of the Nefyrre, east of the desert. There he fouled wells with the bodies of diseased animals. He burned fields when the wind was blowing off the desert, a dry wind that pushed the flames into the cities. He cut down trees. He killed sheep and cattle. And when the Nefyrre patrols chased him he fled onto the desert where they could not follow.
His destruction was annoying, and impoverished many a farmer, but alone it would have done little to hurt the Nefyrre. Except that Cer felt his power over the desert growing. For he was feeding the desert the only thing it hungered for: death and dryness.
He began to speak to the sand again, not kindly, but of land to the east that the sand could cover. And the wind followed his words, whipping the sand, moving the dunes. Where he stood the wind did not touch him, but all around him the dunes moved like waves of the sea.
Moving eastward.
Moving onto the lands of the Nefyrre.
And now the hungry desert could do in a night a hundred times more than Cer could do alone with a torch or a knife. It ate olive groves in an hour. The sand borne on the wind filled houses in a night, buried cities in a week, and in only three months had driven the Nefyrre across the Greebeck and the Nefyr River, where they thought the terrible sandstorms could not follow.
But the storms followed. Cer taught the desert almost to fill the river, so that the water spread out a foot deep and miles wide, flooding some lands that had been dry, but also leaving more water surface for the sun to drink from; and before the river reached the sea it was dry, and the desert swept across into the heart of Nefyryd.
The Nefyrre had always fought with the force of arms, and cruelty was their companion in war. But against the desert they were helpless. They could not fight the sand. If Cer could have known it, he would have gloried in the fact that, untaught, he was the most powerful sandmage who had ever lived. For hate was a greater teacher than any of the books of dark lore, and Cer lived on hate.
And on hate alone, for now he ate and drank nothing, sustaining his body through the power of the wind and the heat of the sun. He was utterly dry, and the blood no longer coursed through his veins. He lived on the energy of the storms he unleashed. And the desert eagerly fed him, because he was feeding the desert.
Emphasis mine.