Wikipedia
Mavka (, , , from ) is Ukrainian mythological female long-haired figure, sometimes naked; a type of rusalkas.
The rusalkas known by this term represented the souls of girls who had died unnatural tragic or premature deaths, particularly unchristened babies. Mavkas often appear in the form of beautiful young girls that entice and lure young men into the woods where they would "tickle" them to death. Mavkas have no reflection in water, do not cast shadows, and have "no back", and so their insides can be seen.
They were believed to live in groups in forests, mountain caves, or sheds, which they decorated with rugs. They made thread of stolen flax and wove thin transparent cloth for making clothes for themselves. They loved flowers, which they wore in their hair. In the spring they planted flowers in the mountains, to which they enticed young men, whom they tickled to death. On Pentecost (known as Mavka's Easter, ) they held games, dances, and orgies. A demon accompanied them on a flute or pipes.
To save a dead unchristened baby's soul, one had to throw up a kerchief during Pentecost holidays, say a name and add "I baptise you". A rescued soul would then go to heaven. If a soul lived up to seven years and did not go to heaven, a baby would turn into a mavka and would haunt people.
Mavkas are depicted in literature, most notably in Lesia Ukrainka's " The Forest Song" and Mykhailo Kotsiubynsky's " Shadows of Forgotten Ancestors".