Forty short tales about the ruler of the thirties - Koshchei, designed to teach adult and young readers how to manage a state, a company or a class of middle schoolers. It turns out that Koschey is so thin because he is a supporter of a healthy lifestyle. So stingy because running the state requires a lot of money. And he’s so old – well, simply because he’s been living for a long time. Koschey is not limited to thirty, but freely visits a wide variety of cities in Russia, and not only in Russia. Koschey loves beautiful ladies, is partial to the cat Bayun, who guards the borders of Lukomorye, and if he occasionally casts a spell, it is only a little and not very much. However, when necessary, he is able to repel the cannibal, the Baba Yaga, and even a practicing doctor-professor. In general, as befits any true sovereign, he is careful, diplomatic and secretive.