Rusalka, the Drowned Virgin

In Slavic mythology, a rusalka  was a female ghost, water nymph, succubus or mermaid-like demon that dwelled in a waterway.
According to most traditions, the rusalki were fish-women, who lived at the bottom of rivers. In the middle of the night, they would walk out to the bank and dance in meadows. If they saw handsome men, they would fascinate them with songs and dancing, mesmerise them, then lead the man away to the river floor to his death.
The stories about rusalki have parallels with those of Hylas and the Nymphs, the Germanic Nix, the Irish Banshee, the Scottish Bean Nighe and the Romanian Iele. See Slavic fairies for similar creatures.

Origin
In most versions, the rusalka is an unquiet dead being, associated with the "unclean force". According to 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, must live out their designated time on earth as a spirit.
The ghostly version is the soul of a young woman who had died in or near a river or a lake and came to haunt that waterway. This undead rusalka is not invariably malevolent, and will be allowed to die in peace if her death is avenged.
Rusalki can also come from unbaptised children, often those who were born out of wedlock and drowned by their mothers for that reason. Baby rusalki supposedly wander the forest begging to be baptised so that they can have peace. They are not necessarily innocent, however, and can attack a human foolish enough to approach them.

Description
While her primary dwelling place was the body of water in which she died, the rusalka could come out of the water at night, climb a tree, and sit there singing songs, sit on a dock and comb her hair, or join other rusalki in circle dances (Russian: ????????, Polish: korowody) in the field.
Rusalka by Ivan Bilibin, 1934
Though in some versions of the myth, the eyes shine like green fire, others describe them with extremely pale and translucent skin, and no visible pupils. Her hair is sometimes depicted as green or golden, and often perpetually wet. The Rusalka could not live long on dry land, but with her comb she was always safe, for it gave her the power to conjure water when she needed it. According to some legends, should the rusalka's hair dry out, she will die.
Rusalki like to have men and children join in their games. They can do so by enticing men with their singing and then drowning them, while the children were often lured with baskets of fruit. Men seduced by the rusalka could die in her arms, and in some versions hearing her laugh could also cause death. Alternatively, they would attract men, mainly bachelors, and tickle them to death.
Specifics pertaining to rusalka differed within regions. Although in most tales they lived without men, in Ukraine they were often linked with water, while in Belarus they were linked with the forest and field. Where land was fertile, the maidens appeared naked and beautiful. In harsher areas of Great Russia, they appeared as "large breasted amazons" (Hubbs). And often, in the north, they were ugly and covered in hair.

Rusalka Week
The rusalki were believed to be at their most dangerous during the Rusalka Week (Rusal'naia) in early June. At this time, they were supposed to have left their watery depths in order to swing on branches of birch and willow trees by nights. Swimming during this week was strictly forbidden, lest mermaids would drag a swimmer down to the river floor. A common feature of the celebration of Rusal'naia week was the ritual banishing or burial of the rusalka at the end of the week, which remained as entertainment in Russia until the 1930s.
Max Vasmer notes that the very word rusalka originally referred to the dances of girls at Whitsuntide. The word is derived through Greek ???????? from "rosalia", the Latin term for Whitsuntide week (originally it meant "the festival of roses").

In Fiction
A rusalka makes an appearance in the adventure game Quest For Glory IV: Shadows of Darkness, and is the spirit of a murdered, unmarried woman. She is confined to the lake where she died, and will drown the hero unless he befriends her.
In the videogame Devil May Cry 4, the protagonist Nero is approached by two glowing blue, beautiful women who attempt to seduce him and lower his guard. The are actually attached the ends of antennae on the demon Bael, who upon being defeated, relinquishes an item called the Rusalka Corpse. Perhaps as a nod to their tradition of dwelling in water, they have a gelatinous quality to their bodies and make slippery, watery sounds when attacked and during the related cutscenes.