The Slavic languages are spoken over the widest geographic region of any language group, except for English and Spanish which have spread from Europe to the Americas and the Pacific. This means that there is a huge amount of information on Slavic-speaking Paganism spread through some 13 countries with additional isolated populations in other countries, including substantial communities of immigrants in the USA.
Geography and History
Slavic-speaking people first appear in the written record in references to the Schlavoni tribes in western Russia by Herodotus. By the time historical records are more complete, around 400-700 CE, the Slavic-speaking people lived in the whole of the Balkan area, Ukraine and Belarus, northwestern areas of Russia and west in Poland, the Czech Republic, and east Germany. It is not known how far east the Russian-speaking people lived at the latitude of Moscow, but they seem to have migrated eastward continually over the centuries. In many of these areas, especially the Balkans, there were substantial communities of people who spoke other languages, some well-known, and some now extinct. Archaeological finds are extensive for these areas, but as there is no writing found in these early sites, it cannot be determined with certainty what languages were spoken in which community.
Religion
The ancient Slavic religion can be seen to be a development of the Proto-Indo-European religion. The same elements in cognate form are found in both. We do not have an early corpus of texts of the Slavic Pagan religion as we do for say Greek or Latin. Most of the earliest written references to Slavic Pagans are brief and inaccurate references made by Christians. However there is a vast amount of folk customs, poetry, songs, dances and stories which carry Pagan ideas and traditions. These confirm the ancestral relationship of Slavic Pagan religion with the larger Indo-European Religion.
Primary Sources
The Russian Primary Chronicle, attributed to Nestor, is one of the earliest written sources and lists the pantheon of Pagan Gods of Vladimir in 980 CE, the time of nominal conversion to Christianity. This is typical of Christian sources and does not provide much accurate information, mainly the bare names of some of the Gods and Goddesses. Other authors who give information about Slavic Paganism from a Christian point of view include Thietmar of Merseburg, Helmold the Saxon, Adam of Bremen and Saxo Grammaticus, none of whom actually spoke a Slavic language.
One early source is the Lay of Prince Igor which was at first thought to be a late (18th century) forgery, but it is now known to be an authentic composition of the 12th century. It can be read as the Tale of the Armament of Igor in a rather difficult translation on Sacred Texts, but this has both the Russian and English side by side. Although the people in this story were nominally Christian at the time, there are many references to Pagan Gods in this beautiful tale which gives a more or less historical account of a military campaign.
These early sources do not give much information but the folk tradition is a different matter. Although folk traditions were collected relatively late, mostly in the 1800's up to the present, they are very extensive and have been well documented and preserved. One of the earliest examples of the folkloric collections is the Songs of the Russian People by W. R. S. Ralston in 1872, which can be found on the Sacred-Texts Archive. These aren't songs and most are not Russian, but they are charming and suitable for children. They take for granted customs like honoring trees by tying a ribbon in the branches, a custom widespread among Indo-Europeans.
Slavic Pantheon
The following list gives some of the more important Slavic deities known from older sources. Almost all of these are easily identifiable as Slavic cognates of other Proto-Indo-European Goddesses and Gods. The names used here are just some of the forms of the names which vary widely because of dialect differences in the Slavic languages as well as differences in the alphabets and the manner of their transcription from the Cyrillic alphabet. The element -bog seen in several of these names means 'a god' in various Slavic languages. The earliest references to specific deities are to Vladimir's pantheon, the Gods and one Goddess worshiped by Prince Vladimir in about 980 CE before his conversion to Christianity. Most of the earliest references are from Christian sources and do not give much information, and even that is suspect. However many of these deities continue to be worshiped in the dual religion of the country people, and so they are well known from folk traditions.
Belbog, with the element bel- meaning 'bright, white.' This deity is known from early Christian sources.
Bereginya, mentioned in old sources, the bereginyi (plural) receive offerings among the folk, and there are folk stories told about them. Bereginya dolls are still made by Russians.
Dazhbog, a 'Day God' known from Vladimir's pantheon and other early sources. In myths, he is the father of the morning and evening stars and of the Zoryi.
Khors, known from Vladimir's pantheon, but little else is known about this God.
Koliada, the Goddess associated with the winter solstice and possibly a personification of it. There are many songs and dances known for her.
Kupalo/Kupala, a deity associated with the summer solstice. Kupalo, a masculine form, appears in early Christian references, while Kupala, a feminine form, appears in more recent folklore sources.
Lado/Lada. Lado, a masculine form, appears in early sources and is identified with Pluto and was the God invited to any occasion of merriment including weddings. Lada, a feminine form, appears in many folklore sources and is the Goddess associated with the May Day festival. There are many songs for her which people still sing. Although the linguistic relationship is uncertain, she appears to be the Slavic version of the Proto-Indo-European Goddess *Pleto.
Leshii, a personification of the forest fires which were a big concern for people who lived and worked in the northern forests.
Marzanna, a Grain Goddess known from early references and later folklore.
Mesyats, a personification of the Moon, Mesyats appears in folk tales, where he or she marries Dazhbog, and they have lots of little baby stars together.
Mokosha, a Goddess from Vladimir's pantheon, she remained important to people and is associated with water.
Perun, known from Vladimir's pantheon, he is the Slavic version of the Proto-Indo-European God *Perkunos, a God of weather.
Poxvizd, Pogwizd are Wind Gods.
Priye and Porevit are Slavic versions of the Proto-Indo-European Goddess *Pria, Goddess of spring flowers.
Radigast at Rethra, known originally from Christian sources, the name Radigast is not well understood, but Rethra, the site of a temple appears to be the Slavic form of a standard Proto-Indo-European Goddess or God. The site of the temple described in old records is not certain, but it is probably south of the Tollense Sea (lake), where a wooden idol (holzidol) with two heads was found in 1968.
Rugavit, known from a confused description by the Christian Saxo Grammaticus, Rugavit was said to be a God of War. In later Slavic folklore she appears as Baba Rugen and similar names, meaning Rye Mother among the country people.
Simargl, mentioned in connection with Vladimir's pantheon, the Simargl was often pictured in folk art as a supernatural bird with a long or braided tail. Various etymologies have been offered, but it may be borrowed from a Zoroastrian/Persian source. The Simargl was also borrowed into Islam and can be found as far afield as Indonesia where it is known as the Simurgh.
Stribog, a Wind God in Vladimir's pantheon, also mentioned in the Lay of Igor.
Svantovit, is mentioned by Saxo Grammaticus but may be borrowed from Zoroastrian as one of the Amesha Spentas. It's not clear because the name has been interpreted and reinterpreted in various languages, including as St. Vitus in Latin. The archaeological site for a major temple of Svantovit has been found at Arkona on the island of Rugen along the Baltic Sea. A proper dig was done by Schuchhardt starting in 1922.
Svarog, a God of the Sun or of the Forge in early sources
Svarozhich, a son of Svarog, another name for a forge or smithy, also known from early sources.
Volos/Veles, though not specifically mentioned in Vladimir's pantheon, it is known that warriors at that time (10th century) swore oaths by Veles and their swords. Veles is more widely known as the protector of cattle though he seems to take the form of a wolf.
Yarovit, one of the faces of Svantovit, and a deity of summer. Yaro means 'summer.'
Zhiva is a Grain Goddess, and the Slavic version of the Proto-Indo-European Goddess *Devi.
Zoryi/Zorya, the Zoryi (plural) were personified forms of the sun at sunrise (dawn) and sunset and their names are cognate with other Indo-European names for the Sun, such as Surya. There is a third sister called Black Zorya who represents Night in folklore. The three are the daughters of Dazhbog.
Many Slavic Gods and Goddesses appear as heroes or heroines in Slavic folktales, and the Slavic deities were also Christianized as saints, often in a quite perfunctory way, by giving them the names of any character that appears in the Greek Christian Bible with hopefully a similar sounding name. As an example of this, it has been widely noted that Perun continued to be worshiped as St. Ilya who was identified with the Hebrew prophet Elijah. However Perun retained his powers, attributes and festival dates. At the same time, Perun was demonized by Christians and appears as a Christian devil in a miniature in the Radziwill Chronicle and in folktales where he is usually a rather friendly devil.
Myths
Some Russian folktales tell stories which are forms of the ancient Pagan myths. For example, the Tale of the Dead Princess and the Seven Bogatyrs was told to Alexander Pushkin by his nanny, Arina Rodionovna, appears to be a cognate with the Grimm tale of Snow White and the Seven Dwarves and is a continuation of one of the oldest Indo-European myths. Folktales and beliefs were sometimes illustrated in the lubki or birchbark books and also in the beautiful lacquer boxes made in Palekh. There is a short version of the Tale of the Dead Princess and the Seven Bogatyrs on this Tradestone Gallery website which also has very pretty pictures of the fairy tales painted on Palekh boxes. Many saints' tales are simply retellings of Pagan myths.
Rites
The common Indo-European practices of worshiping rivers, thanking Goddesses for the grain harvest by garlanding sheaves of grain and wearing crowns of grain, celebrating harvests with circle dancing, songs, and giving Easter eggs, to mention just a few examples, are all well known as Slavic folk-customs. These customs, with their songs and activities, have been extensively recorded by outsiders, by educated natives and now by the participants themselves, especially the dancers and musicians who perform them. Some Slavic Pagan rites are continued in the countryside by people who were never christianized. Many such rituals have been recorded and can now be seen on YouTube.
Festivals
The Slavic festival calendar corresponds with the Indo-European Pagan calendar as it falls out in northern countries, based on the rhythms of nature and of agriculture. In the northern and eastern areas, some of the holidays are compressed into the summer months because of the short growing season. It is possible to reconstruct the entire calendar in great detail because of the isolation of many Slavic-speaking communities which retained traditional ways and also by examining the way in which the Pagan religion absorbed Christianity. This is because in the region of the Greek and later Russian Orthodox form of Christianity, dvoeverie or «dual religion», meaning the combination of Pagan and Christian religion, was more or less accepted even by the church. It is easiest to see the Slavic Pagan festival calendar through the prism of the Christian calendars, such as the Russian Orthodox Church calendars; the calendar of the Old Believers, a very conservative sect of Russian Christians; and through folk lore descriptions of dual religion festivals and customs. This last is especially important for seeing the pattern of women's participation in religion. Women's traditions conserve Paganism because women are excluded from participation in the Christian religion.
References for Slavic Paganism
Most western linguistic scholars do not know the Slavic languages well and much of what is written about Slavic religion by traditional Indo-European linguists is racist garbage. There are a few books in English which address Slavic religion, but most are not very scholarly.
• Indo-European and the Indo-Europeans: A Reconstruction and Historical Analysis of a Proto-Language and a Proto-Culture (Trends in Linguistics: Studies and Monographs 80, 2 Vol. Set), by Thomas V. Gamkrelidze, and Vjaceslav V. Ivanov, with Werner Winter, ed., and Johanna Nichols, translator, M. De Gruyter, Berlin & NY, 1995. This book was originally written in Russian under the title Indoevropeiskii iazyk i indoevropeistsy and it is indispensable for historical linguistics and the relationship of the Slavic languages to the other Indo-European languages. Unfortunately the authors were not much interested in Pagan religion. And a blessing on Johanna Nichols for translating it.
• Poeticheskiia Vozzrieniia Slavian na Prirodu, by Alexander N. Afanas'ev, Izd. K. Soldatenkova, Moscow, 1865 and 1980.
• Gods of the Ancient Slavs by Myroshlava T. Znayenko, Slavic Publ. Inc., Columbus, Ohio, 1980. This is a dissertation, but it is the standard scholarly work in English on the Pantheon.
• Mythology of All Races edited by Louis H. Gray, publ. Cooper Square Publishers, Inc., N.Y., 1916, 1964. Volume 3 is on Slavic Mythology and is by Jan Machal, at Prague. This book is no better and no worse than would be expected for having been written in 1916, though at least it has a Slavic author. It hardly needs to be said, but it is very out of date and does not make use of extensive sources published since that time. Nevertheless many western European authors still quote from it as if it were the ultimate authority.
• Encyclopedia of Religion and Ethics, ed. by James Hastings, Charles Scribner's Sons, NY, 1920. Volume 7, p. 157-159 has Images and Idols [of Slavs], while Volume 11 (eleven), p. 592-595 has a section on the Slavs (religion). This book gives most of the historical quotes from Christian sources in the original Latin and nothing else.
• Mother Russia, the Feminine Myth in Russian Culture by Joanna Hubbs, Indiana University Press, Indianapolis, 1988.
• Organized Pagan cult in Kievan Rus' by Roman Zaroff, © 1995. This is on the internet in two versions, including version I used, but there is a better version with Russian script. This is an intelligent and thoughtful look at the subject.
• Russian Myths by Elizabeth Warner, University of Texas Press, Austin, TX 2002