Origin and appearance
According to Vladimir Propp, the original "rusalka" was an appellation used by Pagan Slavic tribes, who linked them with fertility and did not consider rusalki evil before the nineteenth century. They came out of the water in the spring to transfer life-giving moisture to the fields and thus helped nurture the crops.
In nineteenth century versions, a rusalka is an unquiet, dangerous being who is no longer alive, associated with the unclean spirit. According to Dmitry Zelenin, young women, who either committed suicide by drowning due to an unhappy marriage (they might have been jilted by their lovers or abused and harassed by their much older husbands) or who were violently drowned against their will (especially after becoming pregnant with unwanted children), must live out their designated time on earth as rusalki. However, the initial Slavic lore suggests that not all rusalki occurrences were linked with death from water.
It is accounted by most stories that the soul of a young woman who had died in or near a river or a lake would come back to haunt that waterway. This undead rusalka is not invariably malevolent, and would be allowed to die in peace if her death is avenged. Her main purpose is, however, to lure young men, seduced by either her looks or her voice, into the depths of said waterways where she would entangle their feet with her long red hair and submerge them. Her body would instantly become very slippery and not allow the victim to cling on to her body in order to reach the surface. She would then wait until the victim had drowned, or, on some occasions, tickle them to death, as she laughed. It is also believed, by a few accounts, that rusalki can change their appearance to match the tastes of men they are about to seduce, although a rusalka is generally considered to represent universal beauty, therefore is highly feared yet respected in Slavic culture.