The Deadly Desert is the magical desert that completely surrounds the fictional Land of Oz. On maps, the eastern quadrant of the desert is called the Deadly Desert, while the other three quadrants of desert are called the Shifting Sands, the Impassable Desert, and the Great Sandy Waste.
The desert was originally described as dangerous as any natural desert but no more. Indeed, in The Marvelous Land of Oz, Mombi tries to escape through it and Glinda chases her over the sands, but in Ozma of Oz, it has become a magical desert with life-destroying sands, a feature that remained constant through the rest of the series.
Anyone who sets foot into the sand of any of these deserts turns into sand themselves. The desert is used as a literary device to explain why Oz is essentially cut off from the rest of the world. However, it has been crossed several times by people from within Oz and from the outside world, with applied ingenuity, with magical assistance, or through unusual natural phenomena.
Dorothy Gale is carried into Oz in her house by a cyclone, and back over again by her magic shoes, which fall off during her flight and are lost in the desert.
The Wizard of Oz originally arrived in Oz by a circus balloon (which he implies functioned by a gas lighter than air, rather than hot air), and years later leaves Oz in a hot-air balloon of his own design.
Ozma, the queen of Oz, crosses the desert with her whole court by use of an infinitely unrolling carpet.
In the film Return to Oz, Dorothy Gale crosses the edge of the Desert by stepping upon stones. Later the pack of Wheelers fail to get across the Deadly Desert in pursuit of Dorothy and her flying sofa, who cross the desert to reach the Nome King's mountain. 6 of the Wheelers fall into the desert and are subsequently turned into sand and killed. The 7 remaining Wheelers later return with Princess Mombi and cross the desert through the tunnel dug underneath the desert to reach the Nome King's mountain.