The Luddite Wasteland is a vast and hideous ruin, a remnant of the devastating wars of the Great Old Ones, just past the great wall of Lud. Due to the sadistic nature of Blaine the Mono, Gunslinger Roland Deschain and his Ka-tet are 'treated' to an enhanced magnified view of the hellish valley below and skies above them. It is described briefly but memorably in The Dark Tower III: The Waste Lands, and brought to life in illustrations shown in some editions of the book.
Blasted clean of all but the harshest and most nightmarish forms of life imaginable, it pushed even Roland to the limits of his ability to tolerate the insanity of what they saw. Eddie Dean was immediately disabused of his notion that the Great Old Ones had fought anything as conventional as a nuclear war. It is never stated exactly how these monstrosities emerged, be it biological or chemical warfare, todash escapees caused by the weakening of the beams, or pollution waste from Lud. A later scene in the novels has Blaine's passage destroy an area that has somewhat recovered, so it could be that its passages through this area helped make a bad situation worse, but it is clear that it was the old wars that fashioned the wastes.
The skies above this area were filled with leather-winged creatures that resembled pterodactyls, but which also sported caricatures of Human grins, and also looked vaguely like sting-rays and mantas. In the valley below them, what are ultimately described as pinkish 'stork-things' with long serrated beaks fed on smaller predators that are only slightly less horrid. Other pale mutations are described, but could not be seen with any clarity, for which the Ka-Tet was grateful. With Blaine image-manipulating the train cabin so that it was entirely transparent, the nightmare landscape threatened the group's hold on their sanity without ever being in actual danger (at least from the images; Blaine could have killed them in any number of ways at any time; only his desire for amusement brought them along). Susannah Dean compares what she sees in an organic-seeming red fissure to Tolkien's Cracks Of Doom in Mordor and to Detta Walker's vaguely hinted-at Drawers.
Knowing that if this virtual trip through Hell was taxing him, the others must be near breaking, Roland gambled all their lives on tricking Blaine into an all-or-nothing riddling game they seemingly had no chance of winning, with all participation contingent on Blaine first restoring the cabin to its normal aspect. Intrigued enough by the possibility of amusement and supremely confident of one last victory before ending all their lives, Blaine agreed. Fittingly, the final outcome of the riddling game rested on Eddie using nonsense riddles to push Blaine into complete insanity and 'death', the disorder of the crude riddles doing to Blaine what he sought to do to the Ka-tet with the imagery of the wasteland.