The action takes place on the planet Heim, which is somewhat similar to Earth. From the point of view of the local inhabitants, who consider themselves the most advanced culturally, after the glacial era, which entailed the great fall of society, most of the autochthons of Heim remained mired in barbarism. However, this is a rather cozy barbarism, not burdened with the costs of a theocracy or centuries-long wars, and over the past few centuries, scholastic scientists have managed to restore or rediscover the knowledge of metallurgy, electricity, aeronautics, and atomic energy. Steamships sail the seas, aeroplanes, stratoplanes, and turboplanes ply the skies, and a couple of city-states are building spaceships. There was even a colony established on a neighboring planet. At the same time, scientific disputes are often resolved the old fashioned way—by sword fighting. It may also well turn out that the rocket is being dragged to the launch site by an elephant clad in armor, because a naked local resident, dissatisfied with the noise frightening the animals, can shoot an arrow from the surrounding mountains. All this relative barbaric well-being can quite easily be under threat, for example, due to a volcanic eruption, threatening a new ice age, or an invasion of nomads, or the emergence of a strange chthonic cult... and especially both of these, and a third together.