The Kievan Rus was a federation of Slavic tribes that eventually became the foundation for modern Russia, Ukraine, and Belarus. They adopted Orthodox Christianity in the 10th century, influenced by the Byzantine Empire. Their mythology, before Christianization, included Slavic gods such as Perun and Dazhbog.nnThe Kievan Rus played a crucial role in the spread of Christianity in Eastern Europe, blending their traditional myths with Christian beliefs.