There are still people who are worshiping old "forgotten" faith; in some cases they're being used by political entities who are incorporating Slavic faith under

There are still people who are worshiping old "forgotten" faith; in some cases they're being used by political entities who are incorporating Slavic faith under Pan-Slavism ideology (the further on East in Europe, the more often that happens). In most of the cases the blending between Slavic and Christianity occurred and you can see that Dziady were evolved into All Souls' Day, or Noc Kupały - Kupala Night (Midsummer) turned into St. John's Day and so on. But this is not exclusive to Slavic faith - absorption of cults happened in the history many times when those on a stronger position were conquering those who were weaker. Slavs had to abandon their faith in the face of growing Christianity and baptize, turn themselves into Christians in order to avoid being raided by neighbors and treated as infidels.