Where can one read Russian mythology in english? I always assumed any myths about the "old gods" didn't survive conversion?
You are right, there is no reliable sources about Slavic gods or myths about them. All the “legends” about them and their relations are mystifications and interpretations. Or often it’s just innovations of the neo-pagans.
Even the real facts about Slavic gods are actually quite shaky and incomplete.
For example, the myth of the confrontation between Veles and Perun is actually a hypothesis of the Soviet philologists V.N.Toporov and V.V. Ivanov. They deduced this hypothesis on the basis of three facts:
1.In the Rus'–Byzantine Treatyof 907, the Rus people swore by the gods Veles and Perun.
2. Quite often, the idol of Perun stood on a hill, and the idol of Veles at the bottom of this hill.
3. Veles is associated with serpents and earth. Perun associated with warriors, sky and thunder.
According to the logic of Toporov and Ivanov, these three facts speak of the conflict between Veles and Perun. But many Russian researches criticize this approach for a lack of evidence.
Or, for example, the “myth” about Marzanna/Morana and Yarila (the plot is similar to the story of Hades and Persephone). This myth couldn’t exist among Slavic people because of two reasons:
1. The divine status of Marzanna and Yarila is rather doubtful.
2. Marzanna is a character of the Western Slavs. Yarila is a character of the Eastern Slavs. The deities couldn’t “meet” because they didn’t even “know” each other.










