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 the 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.
The banshee can appear in a variety of guises. Most often she appears as an ugly, frightening hag, but 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 armour of those who are about to die.
Although not always seen, her mourning call is heard, usually at night when someone is about to die and usually around woods. In 1437, King James I of Scotland was approached by an Irish seer or banshee who foretold his murder at the instigation of the Earl of Atholl. This is an example of the banshee in human form. There are records of several human banshees or prophets attending the great houses of Ireland and the courts of local Irish kings. In some parts of Leinster, she is referred to as the bean chaointe (keening woman) whose wail can be so piercing that it shatters glass. In Kerry in the southwest of Ireland, her keen is experienced as a "low, pleasant singing"; in Tyrone in the north, as "the sound of two boards being struck together"; and on Rathlin Island as "a thin, screeching sound somewhere between the wail of a woman and the moan of an owl".
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.