One of the weird beasts of the Great Gray is the Dust Worm. This grey or red-brown creature is, perhaps, a breed descended from the earthworm, though the sages disagree on its true ancestry. They live on organic matter that filters down into the dust, through which they "swim", assisted by a sort of electrical charge they generate that causes dust particles to repel each other. This charging lowers the effective density of the dust, allowing the worm to move through this medium at speeds no mere burrower could hope to match. This "charging" is sometimes visible as sparks in the dust, visible in the short interval between sunset and true darkness. Dust worms retreat from the surface shortly after the sun goes down, to avoid the cold night air, and the rare worm attacks usually happen in that interval. This same electrical sense allows worms to sense living beings on the surface, though large amounts of metal (especially buried metal) tends to disrupt their abilities.
Worms dine on organic matter, including carrion, and they aren't above capturing some on the hoof if the opportunity presents itself. Many small animals avoid venturing out onto the dust for this reason, though anything larger than 5kilograms or so is reasonably safe. Worms normally don't attack large prey, and they usually work alone, though exceptions have been noted. A punishment reserved for terrible crimes among the Dustwalker tribes is to stake a man out on the dust and make tiny slits in his veins - the smell of blood will attract worms from far downwind and they'll gather waiting until the victim is too weak to fight them off.
Ordinary dust worms grow to a length of 3-5 meters, with a full diameter of 10-15 centimeters. Tales are told of terrible sport worms that are large enough to take a hoss in one gulp, but no reliable reports have been made of worms that large.
Worms avoid rocky ground, preferring to range through the deep dust. They congregate in the dunes downwind of settlements, especially if the people are untidy about where they throw their waste or bury their dead, and worm-tangles can sometimes be a danger to stray animals or small children. Many settlements bury pieces of relic scrap around the town to ward off dust worms.