But the most terrible reptile of all that the sand breeds is the dipsad, a snake not particularly big, resembling a viper. Its bite is strong and its poison is thick, causing immediate and lasting pain. It burns and corrodes and sets on fire and its victims scream as if lying on a pyre. But what is

 

particularly wearing and exhausting is indicated by the reptile’s name.
 Dipsad means “the thirst-causing one.” 
 Its victims suffer agonies of thirst, and, strangest of all, the more they drink the greater is their craving for water—their longing increases enormously. It is impossible ever to quench their thirst. Even if you gave them the Nile itself or the whole Ister to drink, you would only add to the burning by watering the disease—like trying to quench a fire with oil.