This is what's written in Arthur Spiderwick's Field Guide to the Fantastical World Around You about Banshees.
Banshees (Family: Circulifestidae?)Edit
Like brownies, banshees are loyal to their households, but rather than help with chores, these eerie and gloomy beings wander the grounds of estates, keening and washing the grave-clothes of those about to die.
Although banshees are described by some as beautiful and by others as hideous, all agree that there is something terrifying about the sight of one. There are even reports that a few unlucky people who have looked into the face of a banshee died of fright. The song of a banshee is similarly lovely and unsettling.
Some believe that preventing a banshee from mourning or refusing to listen to its song will delay death, but this seems unlikely as, in most cases, a banshee is not the cause of death but merely its herald.
- Banshee (Dryas styx?)
Arthur Spiderwick often found that many reports of ghosts are merely the trick of some malevolent Faerie, but in some cases he could not identify with any specific type of Fey. He wrote that "this subject certainly warrants further exploration".
One of Arthur's friends, Albert, told him under his visit to "draw the drapes and not to open the windows under any circumstances". Arthur became confused, because the night was warm and muggy, and he became even more confused when he saw "a white figure darting across the lawn". When he came out, he met a crying girl, who refused to stop and talk to him. She wore on a doll and did apparently also wring blood from a wet rag down into an ethereal bucket and washboard. She floated over the ground at all times.
Arthur later found out that the rag, in fact, was a shirt belonging to Albert's father, who was dying. Both the father and Albert's daughter died in tuberculosis.
Behind the scenesEdit
In Celtic folklore, the Banshee (in Ireland spelled "Beansidhe") is a female Faerie that sometimes is seen keening at the death of an important person. Seeing one is an omen for death. A variation of the Banshee is the Bean nighe ("washerwoman") who can be seen cleaning the clothing for someone who is about to die.
Banshees are in the Harry Potter book the Prisoner of Azkaban. The boggart of Seamus Finnigan, a student at Hogwarts, is a banshee. But, in the Spiderwick Chronicles, banshees help with chores, while the banshees in the Harry Potter series foretell death.
- Arthur Spiderwick's Field Guide (First appearance)