Lost Tomb of Martek (I5), adventure for AD&D 1st ed, by Tracy Raye Hickman
“Skimming across the Skysea, you race against time to save the desert peoples. One thousand years ago, the wizard Martek knew you would come for his Sphere of Power. Are you the heroes of his prophecy or its victims?”
The last module in the Desert of Desolation series (also available as a single volume).