Supernatural beings in Slavic religion

Other than the many gods and goddesses of the Slavs, the ancient Slavs believed in and revered many supernatural beings that existed in nature. These supernatural beings in Slavic religion come in various forms, and the same name of any single being can be spelled or transliterated differently according to language and transliteration system.
Vila (pl. vile, Slovak/Czech víly) is a fairy that is similar to a nymph, identified as a nymph by the Greek historian Procopius; their name comes from the same root as the name of Veles. They are described as beautiful, eternally young, dressed in white, with eyes flashing like thunders, and provided with wings, and blonde hair. They live in the clouds, in mountain woods or in the waters. They are well-disposed towards men, and can turn themselves into horses, wolves, snakes, falcons and swans. The cult of the Vilas was still practised among South Slavs in the early twentieth century, with offerings of fruits and flowers in caves, cakes near wells, and ribbons hung from the branches of trees.
In Slavic mythology, Rusalka is a water nymph, a female spirit who lives in rivers. In most versions, rusalka is an unquiet being who is no longer alive, associated with the unclean spirit (Nav) and dangerous. According to Dmitry Zelenin, people who die violently and before their time, such as young women who commit suicide because they have been jilted by their lovers, or unmarried women who are pregnant out of wedlock, must live out their designated time on earth as a spirit. Another theory is that rusalki are the female spirits of the unclean dead; this includes suicides, unbaptised babies, and those who die without last rites. (Under this theory, male unclean dead were said to become vodyanoy.)
The vodyanoy is a male water spirit of Slavic origin. The Czech and Slovak equivalent is called a vodník, Polish is a wodnik, in Russian it is vodyanoy and vodyanyk in Ukrainian. A South Slavic equivalent is vodenjak. He is viewed to be particularly malevolent, existing almost exclusively to drown swimmers who have angered him by their boldness. Reports of his appearance vary; some tales define him as a naked old man, bloated and hairy, covered in slime, covered in scales, or simply as an old peasant with a red shirt and beard. He is also reported to have the ability to transform into a fish.
The vodyanoy lives in deep pools, often by a mill, and is said to be the spirit of unclean male dead (this definition includes those who have committed suicide, unbaptized children, and those who die without last rites). As previously stated, the vodyanoy would drown those who angered him with boasts or insults. However, there was no certain protection, as the spirit was particularly capricious. Peasants feared the vodyanoy and would often attempt to get rid of the spirit or, failing that, appease him.
The only people who were generally safe from the vodyanoy's anger were millers and fishermen. Millers in particular were viewed to be so close to the vodyanoy that they often became seen as sorcerous figures. This may be influenced by the belief that millers yearly drown a drunk passerby as an offering to the vodyanoy. Fishermen were somewhat less suspect, offering only the first of their catch with an incantation. If a vodyanoy favored a fisherman, he would herd fish into the nets.
Bereginyas (Russian), Berehynias (Ukrainian) or Brzeginias (Polish) are obscure fairies mentioned in "The Lay of St. Gregory the Theologian of the Idols", which has been preserved in a 15th-century Novgorod manuscript. "The Lay" is a compilation of translations from Greek sources studded with comments by a 12th-century Kievan monk. The text, which seems to have been considerably revised by later scribes, does mention "vampires and bereginyas" as the earliest creatures worshipped by the Slavs, even before the cult of Perun was introduced in their lands. No detail about "bereginyas" are given, affording a large field for speculations of every kind.
Boris Rybakov connects the term with the Slavic word for "riverbank" and reasons that the term referred to Slavic mermaids, although, unlike rusalkas, they were benevolent in nature. The scholar identifies the worship of vampires and bereginyas as a form of "dualistic animism" practiced by the Slavs in the most ancient period of their history. According to him, the term was replaced by "rusalka" in most areas, surviving into the 20th century only in the Russian North. After the publication of Rybakov's research, the "bereginya" has become a popular concept with Slavic neo-pagans who conceive of it as a powerful pagan goddess rather than a mere water sprite.
As is common in folklore, there is no standard set of characteristics, or names, and spirits or magical creatures are referred to by many names, often identifying their function or the place or environment of their activity. Such descriptive terms include: