The problem of ethnic religion was not thoroughly investigated by science so far, especially because it concerns the West Slavic tribes whose testimonies speak very few about it. The deficiency of complete descriptions of ancient Slav's life conditions is an inspiration for contemporary literature authors. Jaroš used this deficiency and created a story which purpose was to present the most important problems in life of Slavic tribes at that time; one of them was connected with ethnic religion. The author presents its structure and essence in context of duorumviratum (diarchy): secular, performed by voivode Miliduch and spiritual, performed by spiritual-server Božetěch. Common basis for that duorumviratum appears to be the idea of patriotism which connection with the ethnic religion has not been investigated thus far. Another question is a relation between the religion and nature. The author, in relation to Miliduch's problem, emphasizes the importance of ethnic religion for the ancient Slavs and indicates its influence in the present time with an admonition for the future..