The Avalon--and its inhabitants--portrayed in Gargoyles has its origins in many places. Avalon itself is from the King Arthur mythic cycle. It is the faerie land where Arthur's body is taken to lay until he is to rise again--during England's darkest hour. "Avalon Part III" and "Pendragon" are episodes from Gargoyles that deal with the "Arthur Arisen" legend.
Avalon is the usually considered to be an otherworldly isle, home to druids, faerie, and the Sidhe. Some sources, trying to prove that Arthur truly existed, link Avalon to Glastonbury off the coast of England. The name 'Avalon' comes from the Celtic word Afallach, meaning apples. Apples play a large role in the mythologies of the world, from Christianity and the Garden of Eden, to Greek with the golden apples in the Gardens of the Hesperides, and even British, when St. George slept under the mystic apple tree and was healed of his wounds from the dragon.
In the Arthurian tradition, Avalon is the home of the Lady of the Lake, and the druids that she presides over. Other prominent figures who have made Avalon their home include Morgan le Fay, Nimue and/or Viviane, and even the great Merlin himself. It is retreating further into the mists (hence the title for Marion Zimmer Bradley's Mists of Avalon) that separate Earth from the Otherworld as people turn more to Christianity, forsaking the old ways and calling them the works of the Devil. It is a place of sacred lore for both bards and druids, with magic, mystery, and memories.
In Celtic mythology, Avalon represents one of the many isles of the Tuatha De Danaan. These are the 'Children of the Goddess Danu' and in Celtic mythology, were the first race in Ireland. They were forced to retreat to their fortresses of magic as men and Christianity began taking over Ireland and the rest of Britannia. The Tuatha De Danaan are also known as the Sidhe (pronounced 'Shee') or the 'people of the mounds'. There are a few differences, as the Sidhe are usually considered to be a race of gods and faerie-folk who reside in the Celtic Otherworld: underground, across the ocean, etc.
People probably remember the Banshee from "The Hound of Ulster" and "The Gathering-Part I" episodes. Her name is a bastardization of 'Bean Sidhe' or 'Woman of the Hills'. Her keening wail heralds the death of a family member. Her animosity towards Cuchulain is just a plot element for the show, and not based on anything found in the myths.
That brings us to the inhabitants of Avalon--from Gargoyles at least. As we are looking that them through the prism of the show, the groupings might be slightly different than one would expect. For example, Puck will be discussed with the rest of the trickster Fae, even though he, Titania, and Oberon all come from Shakespeare's Midsummer Night's Dream. We wouldn't want to injure Oberon's touchy honor, right?
Catch the skiff with the rest of the clan back to the homepage.
Hopefully it'll bring you back there without sending you on your own "Avalon World Tour." On the other hand, if a little adventure is what you're looking for, why don't you check out Xanatos and the Links page?