In Celtic mythology, there is a mysterious group of supernatural beings, the aes sídhe, who belong to a realm which is beyond human understanding (yet which lies athwart the mortal world). The greatest among these aes sidhe were gods and goddesses—divine incarnations of nature, time, or other abstract concepts. Other members of the fairy host were thought of as elves, goblins, sprites, or imps (for example, the leprechauns–the disconcerting little tricksters of fairydom). However the supernatural world was also filled with the restless dead…beings who were once mortal but whose failures and miseries in life kept them connected to this plain of existence. A particularly ominous group of these dark spirits comprised the sluagh sidhe—the airborne horde of cursed, evil, or restless dead.
The sluagh sidhe (also known simply as the sluagh) were beings who were cursed to never know the afterlife. Neither heaven nor hell wanted them. Like Jack O’Lantern they were condemned to roam the gray world. Unlike Jack O’Lantern, however, the sluagh were reckoned to be a malicious and deadly force. They appeared en masse in the darkest nights and filled the air like terrible rushing starlings or living mist. One of the most horrible aspects of the sluagh was the extent to which their horde existence erased all individual personality (like eusocial insects—but evil and spooky).
Before the advent of Christianity in Ireland, Scotland, and the northlands, the sluagh were thought of as a dreadful, otherworldly aspect of the wild hunt. When the dark gods came forth to course the world with hell hounds, the sluagh were the evil demons and fallen fairies which flew along beside the grim host. After Christian missionaries began to arrive, the idea of losing one’s soul forever became worse than the idea of merely being torn apart by dark monsters—and the sluagh was reimagined as a force which hunted and devoured spirits.
The sluagh were thought to fly from the west. They were particularly dangerous to people alone in wastelands at night (which sounds dangerous anyway) and to people on the threshold of death [ed.–that sounds dangerous too]. Some of the Irish death taboos against western windows and western rooms are thought to be related to fear of this demonic horde. Although the sluagh could apparently be dangerous to healthy people in good spirits, they seem to have been most dangerous to the depressed, the anxious, and the sick. From my modern vantage in a warm well-lit (northerly-facing) room, the idea of the sluagh seems to be an apt metaphor for depression, despair, and fear. Hopefully they will stay far from all of us!