The world of Faeridor was my first attempt at building a coherent and detailed campaign setting; it began, as many home-made settings do, small in scope then expanding over the course of play. The world was conceived by my desire to explore the dark and capricious nature of the fae, as opposed to the Tolkien-esque elves of high fantasy, and provide a point of origin from which Celtic mythology arose. This was a parallel world to Earth and the dimensional boundaries overlapped in places, allowing inhabitants from one world to cross over into the other.
I considered that mythologies of Earth were the distorted, second-hand view-points of human visitors to Faeridor, or the fleeting glimpses of creatures from that world that slipped into our own. Naturally the concept of Faeridor soon grew beyond a simple study of Celtic mythology and became a point of origin for all of Earth's myths and legends.
Initially, gods did not play a role in my world. I ran the first games in this setting using GURPS, in which all spellcasters can learn healing spells if they want to, so fleshing out the gods was not a priority. Oh, there were clergy, but they were impotent devotees of silent gods. I had always intended the powerful and immortal Tuatha de Danann of Celtic legend to serve as the gods of man, but I never put much thought into them or worked out any sort of cosmological framework for my milieu.
I recently returned to Faeridor, beginning a new campaign set there after a hiatus of over a decade; this time using Castles and Crusades. Since C&C is an AD&D-inspired rule system, I either needed to get off my butt and finally work out the higher powers of my world or eliminate the cleric class and roll all of the spells into the wizard spell list. I opted for the former option, taking the opportunity to finally expand the horizons of my setting and answer the questions I'd been ignoring for the last twenty years. I say 'higher powers' because, although they are powerful, immortal, and worshiped as gods, none are responsible for the genesis of the world or the cosmos, which, to my mind, sets them apart from true deities associated with creation - none of whom exist in my milieu.
The first tier of gods are the Tuatha de Danann, the gods of man. These are the most humanistic of the higher powers, consumed by their own petty concerns and interests, much like those who worship them. The de Danann race once dwelt upon Faeridor, extending their rule across the world, including such domains as the Seelie and Unseelie courts of western Faedun. Powerful mages, capable of interdimensional travel, they frequently meddled in the affairs of Earth and many of them are known to us: Finvarra, king of the Seelie Court, Manannan, Zeus, Thoth, Set, Loki and countless others. Their internecine in-fighting eventually drove them to leave Faeridor and seek out new homes in the cosmos, but although they have long since lost interest in Earth, they continue to meddle in the affairs of their former home and perpetuate their feuds by proxy, lending power to their cults and followers. Philosophically, the Tuatha de Danann correspond to the Great Ones of Lovecraft's mythos - petty, self-absorbed gods; though unlike the Great Ones they remain interested in the affairs of mortals.
The second tier of gods are the Fomori; elder powers who ruled Faeridor before the coming of the Tuatha de Danann. A bestial, primal race of immortals, they fought the de Danann interlopers who eventually defeated them and usurped their position. Over the millenia the Fomori have been all but forgotten on Faeridor, alluded to only in the most profane tomes of ancient lore, but recent hints have been uncovered that suggest a cult devoted to Balor, the Fomori king, has risen again. Other Fomori lords include Baphomet, Orcus, and Demogorgon among others.
The third and most terrifying tier of gods are those primordial powers, beyond human comprehension, that ruled Faeridor in aeons long past. Woe betide the world should any mad cult succeed in waking just one of these from their eternal slumber and draw their attention once again to the world. Lesser beings of this pantheon still exert some influence upon the world: the Caemric druids of Llanvirnesse sacrifice to Shub Niggurath, dark goat of the woods with a thousand young; and the barbarian tribes of the Hoarfells speak in hushed whispers around the feasthall fires of Ithaqua, the windwalker.
I think I've finally gotten the cosmological mix just right; it cleaves to the real-world mythology upon which the setting was originally based, while incorporating Lovecraftian mythos and iconic demons of D&D in a mix that is just to my taste.
Now to put them into play.
Welcome Back to the Labyrinth
"We have been away far too long, my friends," Ashoka declared, his face lit by the eldritch green glow of his staff. "But we have finally returned to the labyrinth whence our adventures first began."
"Just imagine the treasures that lie within," said Yun Tai, flexing his mighty muscles. "Wealth enough to live in luxury the rest of our days."
"And arcane artifacts of great power," added Ashoka his words dripping with avarice. "All ours for the taking!"
"Umm...guys?" Nysa interrupted. "Do you hear something dripping?"