This is a link to a video that our faculty advisor sent me. It discussed "a small nationality inside Russia that has preserved it's original religion despite 1000 years of often violent attempts to "Christianize" them. The Mari people are not Russian or even Indo-European (they are distantly related to the Finns and Estonians) but most elements of their religion look familiar enough." I have not yet gotten the chance to watch the entirety of the video, but it should prove quite interesting.