Grinning Skull Oasis
This grimly-named oasis in the Plains of Purple Dust has an equally grim history. Established when the desert was closing over the once fertile lands, the Manetho empire transformed the only well in the region into a deadly trap. Now it stands in the desert, a sole promontory weathered into the rough outline of a skull, surrounded by six shimmering pools.
Knowing the oasis was necessary to travelers, whether merchants or army, the wizards of Manetho magically changed the water of the well into a poison deadly to creatures but harmless to plants. At the same time, they could not completely destroy the oasis, since their own people needed its water to reach the outside world.
Thus, they divided the flow of water into a series of six pools. The water from five of these can kill instantly. The sixth pool is harmless. The water from all six is clear and sweet-tasting. As the final touch to their evil deception, the wizards altered the oasis so that each morning a different pool was safe to drink.
Although logical minded people reason the wizards must have set some pattern for this change, no one has discovered any sequence yet.
The oasis is not deserted, however. A group of desert bandits led by Sheik Ar-Rabi has made this their base. They have a simple solution to their drinking water problem. When they need to refill their cisterns, prisoners are forced to drink from the pools until the safe one is found. When necessary the Sheik uses desert lizards, dunking the little creatures into the pools. “The lizards are equally accurate, but the Sheik far prefers human victims.