A common mistake when writing adventures set in deserts is to assume that the climate is too ferociously hot to wear armor. Historically, most battles in deserts involved troops dressed in protective armor. Although they would have been miserable during the hottest part of the day or the hottest part of the year, desert weather isn't intolerably hot 24/7.
A legend tells of a people living deep in the desert, they appear at first as ordinary human beings, sometimes impersonating someone familiar to the PCs, before causing their features to disappear, leaving a blank, smooth sheet of skin where their face should be.
The PCs come across a town with a strange curse: Every morning, those who have grown up here wake up with the memories of someone else. They do not find this strange and have no idea it is happening. They calmly wake up and start these new lives as though they have always been that way.
The cause: A wizard who lived there was spurned by a maiden he was infatuated with. His attempt to manipulate her memories into believing they were already together and that she loved him went horribly awry.