A Thrax is a dreadful creature that exists by draining the water from its victims. The thrax is very intelligent and is an implacable foe. The thrax is humanoid in appearance with a ruddy tinge to its skin. It has dark hair and pointed ears, but it will never be mistaken for an elf. Its features are gaunt and angular, and the eyes of a thrax are a deep blue, like a pool of water. The thrax is a muscular creature; it has long thin arms and fingers that end in small suckers. Thrax speak all of the languages they knew in their former existence.
A thrax needs to feed on a victim at least once a day. A thrax can drink water, but it does not provide the nourishment that he requires.
A thrax prefers to attack solitary creatures, either a being out by itself or perhaps a lone sentry on watch over a sleeping camp. The thrax uses its shadow-form to close with the potential victim, solidifying behind him. If the victim is well armored, the thrax will attempts to decay the victim’s armor. When the armor falls to pieces around the victim, the thrax attacks with its powerful arms, to hold and drain the victim of all the water in his body.
The thrax is an unfortunate creature that can be found anywhere. Since the corpse of a thrax victim is unmistakable, thrax are not common in cities or villages, at least not for long. They usually leave as soon as they discover their curse, or else they are hunted down and wiped out. Outside the villages they lead solitary anguished lives. The thrax remembers what he was like before the change, but he cannot help himself. He is driven to try to survive. At first, the new thrax may even retain his original alignment, perhaps resolving to feed on animals instead of intelligent beings. But the curse continues to work, and after a few months, feeding is the only thing that matters. He also begins to hate those who have not suffered his curse, especially humans and demi-humans.
Walter Baas (March 1992). Terrors of the Desert (Dark Sun Monstrous Compendium I). TSR, Inc. ISBN 1-56076-272-1.