Men who had died in storms of the Great Desert had been known to linger on in Middle-earth as tortured spirits known as Sand Devils. They maintained a semi-material form with the appearance of miniature, sand-choked whirlwinds, and traveled across the open wastes of the desert searching aimlessly for lives which they could end. Their form also made for perfect camouflage in their environment, since ordinary whirlwinds were not at all uncommon in the region.