An area in the Desert of No Return filled with shifting sand that, once on you, tunnels its way into your body and suffocates you.

There is a djinn controlling the sands: Hafardiz. He is an ancient guardian of Zohzōtimani; only those worthy enough to pass the test of the Dancing Sands can gain entry to the buried city. Hafardiz is not malevolent, but he has a high opinion of himself. The sands are a test - any who cross are halfway to proving themselves worthy. (You could also just speak the ancient password of Zohzōtimani, if Queen Abilani was kind enough to share it with you . . .)