Also Banshi and Benshee, Irish and Scottish in origin. A female death omen spirit that manifests to herald approaching death with wailing. The word is derived from the Old Irish ben sidhe, a woman of the fairy mound, or woman of the fairy mound, but it is translated by different scholars in a variety of ways, including Female Fairy, Angel of Death, Lady of Death, Woman of Peace, White Lady of Sorrow, Nymph of the Air, and Spirit of the Air, amongst others.
Many people have described the terrible wail, which precedes a death, and certain families are traditionally believed to be followed by the Banshee. The word is sometimes also used to denote assort of demon, but in Nordic folklore the Banshee is always benevolent.The Banshee of legend is actually a disembodied soul, either of someone who in life was strongly attached to the family or who hated all its members. So, if she loves those whom she call, the wail is soft, tender, soothing chant, intended to either give notice of death's proximity or reassure the one destined to die, or to comfort the survivors. But if instead the Banshee during her life was a enemy of the family, the wail is more like the scram of a fiendish ghost, a demonic howling of delight over the coming fatal agony of one of her foes.
John's Journal: The Banshee
Banshees are death omens, but they might also harm their own. John describes them as either dressed in white or in a sheet or burial gown, and they come in the form of a beautiful woman, a matron, or a hag - these stages correspond to the stages of womanhood (John thinks this might also have to do with the age of the person who's going to die). The Banshee can be seen at rivers, washing bloody clothes.
The Black Annis (one-eyed, features of a demon, claws, blue face) was said to hide in an oak; she was a cannibal who preferred children. The Baba Yaga (a russian Banshee) lives deep in the forest in a magical hut. While the Baba Yaga also eats children, she's also supposed to be a source of magical help.
In the first installment of the Supernatural novel series, Nevermore, while solving the Edgar Allen Poe case, the boys also have to tangle with a Banshee for one of Ashes' friends. However, she didn't want vengeance, she wanted justice. So Sam and Dean lay her to rest by making her killer confess and leaving him for the cops.
Banshees in Lore
The story of the bean-sidhe began as a fairy woman keening at the death of important personages. In later stories, the appearance of the banshee could foretell death. Banshees were said to appear for particular Irish families, though which families made it onto this list varied depending on who was telling the story. Stories of Banshees were also prevalent in the West Highlands of Scotland.
The banshee can appear in a variety of guises. Most often she appears as an ugly, frightening hag, but she can also appear as a stunningly beautiful woman of any age that suits her. In some tales, the figure who first appears to be a "banshee" is later revealed to be the Irish battle goddess, the Morrígan. The hag may also appear as a washer-woman, or bean-nighe (washing woman), and is seen washing the blood stained clothes or armor of those who are about to die. The banshee may also appear in a variety of other forms, such as that of a hooded crow, stoat, hare and weasel - animals associated in Ireland with witchcraft.
The most famous Banshee story is the Brother Grimm fairy tale Hänsel and Gretel, in which two children walk into the woods where they are caught by an old hag, who prepares to eat them.