Like the other Indo-European peoples the Slavs shared a hierarchy of gods and spirits, some benevolent and others malevolent, which governed every aspect of their lives and sought propitiation requiring the expenditure of much effort through private and public worship and ritual. Paramount in the ancient Slavic pantheon was Svetovid, god of fertility and war, who shared his primacy with Svarog, god of heaven and the air. The latter's son, Svarozid, was god of fire. The two in relationship and function resembled Zeus and Hephaestus in ancient Greek mythology. Among the Eastern Slavs Perun, the god of thunder and lightning, enjoyed high rank like Thor in Germanic mythology. After the Eastern Slavs were converted to Christianity Perun was eventually absorbed into the personage of St. Elijah seen in Russian iconography riding a chariot of fire across the heavens. Important also were Chernobog, the black god of the underworld, who survives in many Slavic curses, and Belobog, the white god of the upperworld. The two displayed that dichotomy of good and evil found everywhere in Indo-European religions, which manifested itself later in the growth of the Gnostic heretical sects in the early Christian period.

In addition to the above dieties there were many spirits of lesser importance whose characteristics and functions came to vary considerably among the various Slavic tribes. They inhabited animals, plants, trees, rocks and rivers and placed great demands on the ancient Slavs who sought to propitiate them. Among them was the "unclean spirit" (Nechysta Syla) relevant especially to this web page in supporting the custom among Eastern Slavs to place healing willow branches behind icons and crosses to augment the latters' ability to repel evil from the household. One dare not forget the infamous Baba Yaga who lived in darkness and devoured people. This demonized goddess or witch is well known in Russian folklore and verse and is commonly used to frighten children into obeying their parents. Baba Yage bears a striking similarity to Kanahora, the evil eye of the Eastern European or Ashkenazi Jews.

Ancient Slavic religion was quite unsophisticated and naturalistic. It contained neither doctrines nor creeds nor scripture nor organized priesthood. Above all it was like all other Indo-European religions in being completely non-ethical, demanding of the people no system of specific conduct deemed to be pleasing to the dieties. Its practice was completely ritualistic, i.e. it provided the people with a system of rites for the propitiation of the gods whether good or bad. That system of elaborate rites and sacrifices in private shrines was sometimes accompanied in public temples by human sacrifices and exercised a firm hold on the Slavs long after they were converted to Christianity.

The pre-Christian Slavs were not literate and left no written records about their culture and religion. What we know about the pre-Christian Slavic religion, other than that from analysis of archeological finds, came from the West in the writings of German missionaries bearing Roman Christianity and from the South from Greek monks bearing Byzantine Christianity. Both the Eastern and the Western churches held to the belief that Slavic heathenism was of demonic origin and entirely without merit. When Christian missionaries encountered the Slavs they found religious practices entirely different from their own. Christianity contained a fullness of doctrines and creeds as well as customs or religious practices derived from and supporting the fundamentals of the faith. Moreover Christianity had an ethical system of behavior derived from the religion and illustrated through scripture and other writings. In other words, Christianity was both doctrinal and ethical. Slavic religion was neither. As elsewhere when paganism encountered Christianity it resisted but the old religion was eventually overcome by the new which incorporated into it some of the old right into modern times. This subject will be covered more fully in the essay which follows dealing with the conversion of the Slavs.