Wraiths and Seductresses
An unfortunate consequence of the Christianization of the Celts was that the spirits of the earth, especially female ones, began to take on a sinister cast, becoming evil seductresses, wraiths, and monstrous hags. The tests of the goddess became mere bloodsport for monsters who inhabited the forests, lakes, and streams.
Originally, the banshee, or ban Sidhe, was at one time simply a female of the Sidhe, or fairy-folk. Over time, however, the name came to signify a very specific type of unlucky spirit. Because an encounter with a fairy meant that one was literally “walking between worlds,” she came to be viewed as an omen of death.
In later folklore, the banshee evolved into a sort of wraith or ghost, often attached to a particular house of family, whose bloodcurdling wail meant the impending death of a member of the household.
The Washer Woman
A related spirit to the banshee was the ban nighe, or “washer woman,” a character encountered in Irish and Welsh mythology who also came to be viewed as a shade. The ban nighe was originally a particular aspect of the goddess of sovereignty, who symbolically washed the garments of a warrior and warned him of his impending death. In Christian times, she lost her divine aspect and became an apparition who would appear beside the river, washing the grave clothes of those about to die.
An early version of the washer woman myth concerns the Welsh sovereignty goddess Mabon, who is inexplicably cursed to wash at the river-side until she bears a son by a Christian. That son is the hero Owain, and the tale was probably symbolic of the passing of dominance over the land from pagan to Christian.
Romanticized tales of the washer woman give a more benevolent aspect to the water goddess. In many cases, she is a mysterious lady who guards a well, stream, or fountain, and whose function is to test the hero or provide him with a task, quest, or geas.
While the banshee and the ban nighe were not viewed as malevolent, there were creatures who could cause the death of any unfortunate enough to cross their paths. The most malevolent of these was the korrigan, originally thought to be the spirits of female druids who opposed the conversion of Celtic lands to Christianity. She is especially associated with water, and may be another aspect of the Morrigan. There are generally said to be nine korrigans in all.
The korrigan was a wicked spirit, with a number of vile habits. She was fond of sitting by the lakes or wells, combing her long, beautiful hair, and she would attempt to seduce any man who chanced by. Those who spurned her advances would be cursed with death.
Men weren't the only victims of the korrigan. It was she who was largely credited with the kidnap of human infants, replacing them with change-lings, and raising the human children as her own.