Bies
Region of origin: Eastern Europe and Russia
Primeival nature spirits in Slavic mythology, the biesy were malevolent entities born of the evil of the forests and dark places of the earth who tormented humans that had dared venture there, attacking them or possessing them and driving them mad. A wild animal who was making the sounds of another species was a giveaway that it was a bies in an assumed form. As Christianity entered the region, “biesy” came to be more associated with general evil spirits and was used synonymously for lesser devils and demons.
The Compendium of Arcane Beasts and Critters 