In the mid 1300's DR, the Grinning Skull oasis served as the base for a group of bandits called the Desert Wind. They were led by Sheik Ar-Rabi. The bandits forced prisoners to drink water taken from the pools in order to determine if the water was safe. Desert lizards were used if there were no prisoners on hand.
This well was established during the twilight years of the great Imaskari Empire. The Imaskari decided to turn the only well located in the region into a dangerous trap. The pure water from the well was changed into a poison that was deadly to animal life but harmless to plants. The water from the well was diverted into six separate pools. Five of the pools carried the poisoned water and one remained clean. The water from all of the pools looked and appeared identical to the others. True to their cruelty, the Imaskari cast an enchantment upon the pools so that the safe pool would randomly shift with each sunrise.