The book is dedicated to the “lower” mythology of the Slavs, i.e., popular beliefs about the characters of evil spirits - mermaids, witches, brownies, the spirit-lover and spirit-diviners, etc. Problems related to the difficulties of identifying demonological characters are touched upon and with the development of methods for the comparative study of demonology of different Slavic peoples. When studying this most important fragment of folk culture, the main thing for the author remains the fact of the inclusion of mythological characters in all spheres of everyday and ritual life of traditional society. The Appendix publishes for the first time field materials from the Polesie archive, containing folk beliefs about mermaids. The book is intended for a wide range of readers interested in folk culture, folklore and mythology of the Slavs. Folk Demonology and Mythoritual Tradition of the Slavs The book is dedicated to the Slavic folk mythological characters, such as “rusalka”, witches, house-spirits, demon-prophet, demon-lover and so on. The author studies the problem of the identification of mythological beings and comparative study of the demonological systems in Slavonic beliefs. The principal point of research is to realize that every mythological character is included into the whole sphere of people’s ritual and everyday life. The Supplement provides new materials from the Polessian-Archive on the people's beliefs about “rusalka”. The book is intended for the general readers, who are interested in the folk culture and Slavic mythology.