cybertalus said:
Finally the Cu Sith (coo shee), which I think appeared somewhere in D&D as an "elven dog" was a Highland dog with shaggy green fur, a long tail, and large feet. The Cu Sith were said to be as large as a two year old bull. They moved very quietly along the ground, not barking constantly while hunting, but occasionally baying loudly, and left large distinctive footprints in mud or snow.
These are another standard British folkloric theme - the MM's yeth hound is an adaptation of the Dartmoor version. Hound of the Baskervilles too.
Some of them have already been mentioned , but the general classes of British (which is effectively "Celtic") supernatural beasties would have:
* Prankster fairies - (e.g. spriggan, fear dearg, pucca/puck) - Activities would range from fairly harmless tricks to violent hooliganism (apparently they're fond of soccer). In many stories, they're particularly likely to molest the antisocial, the mean-spirited, and the unreligious, especially people skipping Sunday services.
* Serving fairies - (e.g. brownies) - Said to perform small household chores in exchange for small tributes, like a saucer of milk set out every morning. In some stories, they harass new residents who fail to keep up the bargain.
* Dancing fairies - Troops of fairies that throw various sorts of wild parties in remote areas, often at stone circles and other mysterious ancient monuments. Mortals witnessing these are often punished in some way if they reveal their presence, though occasionally the fairies will take a liking to someone, which can be even worse. Most "fairy mound" stories involve this type of fairy.
* Changelings - Fairies that steal human children and take their places so as to mooch off of unsuspecting parents.
* Drowned maidens - usually malevolent or at least unfriendly water spirits, which are generally said to be the ghosts of young women who drowned in and now haunt a particular river or body of water. These often are attributed typical human names like "Peg Powler." Sometimes they attempt to drown people, but in most stories their main function seems to be simply acting frightful.
* Water horses - (e.g. each uisge, kelpie) Almost always evil. A common MO is for the creature to take the guise of a horse and to wander around until some unsuspecting human sees the fine animal unattended and decides to make off with it. The back of the water horse is however adhesive, and so the horse dashes for its nearby watery home with the hapless rider stuck on its back. These tales often note that only the victim's liver is ever seen again. These are probably a subclass of an older genre of river and lake monsters which appear in medieval sources. Generally in the older versions, the monsters tend to be serpents or serpentine and are a lot less subtle in their methods. A good example is the
Life of St. Columba, which depicts St. Columba actually turning a monster (D&D cleric style) in the River Ness with his crozier.
* Heath hounds (noted above) - Usually big scary dogs that appear in such places as remote moors and along foggy lanes at night, though like the drowned maidens, their main literary function seems to be to scare the bejeezus out of people. Sometimes these are held to be prankster fairies getting their jollies from frightening local rubes.
* Premonitory spirits - (e.g. banshees, fetches, grey man) - Strange spirits which foretell death and disaster by their appearance. Banshees are particularly noted to belong to particular families. Sometimes these are said to be the ghosts of real people, as with the drowned maidens.
* Wereseals - (e.g. selkies, roans) Seals who can remove their own skins to reveal human bodies. Typical story involves a man stealing the skin of a beautiful selkie woman so she can't return to the sea. They're usually non-threatening and sometimes even friendly if treated respectfully (generally true of fairies). They're sometimes credited with saving shipwrecked sailors.
* House haunts - Ghosts that haunt particular structures, should be pretty familiar.
