Slipsand

Athas’s acute heat can cause an elemental reaction in sandy areas where magic, primal power, or psionics have been used heavily. The ground becomes saturated with high quantities of glass particles, making its surface particularly treacherous.

    Effect: A creature that enters a square containing slipsand must make an Acrobatics check (moderate DC). On a failure, the creature falls prone and takes 5 damage per tier from the glass fragments.
    Usage: Creatures not trained in Acrobatics, particularly those that have low Dexterity scores, are greatly inhibited by slipsand. This terrain should be used judiciously, since it can drastically reduce mobility in an encounter.

Published in Dark Sun Creature Catalog, page(s) 137.