Elves (The Elvenpath)
The Elves (Old Albic Elbi) are the focus of an incipient legendarium named The Elvenpath, by Jörg Rhiemeier. They are not really a separate race, but humans with an 'Elvish' culture (similar to Tolkien's Elves). They were the bearers of an ancient civilization that existed in the British Isles before the immigration of the Celts, and are the source of the Germanic and Celtic traditions of elves (hence 'Elves'), as well as the Greek tradition of Hyperborea. It is possible that the Atlantis myth is partly based on a memory of the civilization of the Elves, too, as the geographical description of Atlantis matches Britain to a fair degree.
While tending to be tall and slender, they look like normal humans of European origin (that means that they don't have large pointed ears or any other non-human features commonly associated with 'elves'). They speak Albic languages; in Old Albic, they called themselves Elbi (singular Alba). This self-designation was borrowed into Germanic as *albiz, hence English elf. The old Celtic name of Britain, Inis Albion, means 'Island of the Elves'.
The classical Elvish civilization
Elvish society was egalitarian, liberal and democratic. There never was an 'Elvish empire', only a loose confederacy of self-governed polities, the Commonwealth of the Elves (Samvarda ela Albela). The British Elves were great mariners and sailed the Atlantic, establishing tradeposts along the shorelines.
The Elves believed that the purpose of humankind was to preserve the world and enrich it by creating new and beautiful things, and that in order to fulfill their Purpose, people had to be free. The social ideal was that of the free-lance artisan.
The anicent Elvish religion, Macavenism, combined monotheistic and polytheistic concepts. Supreme was the creator god Éa 'The One', who was believed to be immanent in everything. (Note that the name Éa is of common gender, neither male nor female.) On the second tier, there were twelve deities (six male and six female) called the Macaveni 'Great Spirits', who functioned in a similar way as the Greek, Roman, Celtic or Germanic polytheist pantheons, and were the addressees of most practical worship, while Éa was more of a philosophical concept.
The Elves used a lunisolar calendar based on the Metonic cycle (19 years = 235 months); the year 1 of the Elvish calendar was the year 1823 BCE, the date of their legendary landtaking. This is actually based on the date of the foundation of the Commonwealth which was in 671 BCE and said to have happened 'eight gross years after the landtaking'. The year began on the first new moon after the winter solstice.
Elvish astronomy was highly advanced, and Elvish scholars developed a 'Copernican' cosmology, with the planets (including the Earth) orbiting the Sun rather than the Earth, more than 300 years before Aristarchos of Samos.
Elvish philosophy of nature was similar to modern morphic field theory. Every living being has a soul (nâra), and even inanimate objects have a phanara, a kind of form-giving entity, gestalt, or morphic field that resonates with other phaneri. Everything, from the whole universe down to the smallest particles of matter has (or rather, is) a phanara, and thus the universe is a grand hierarchy of nested phaneri; a nâra is an especially strong phanara specific to an individual being.
The Elvish civilization reached the peak of its development around the year 600 BCE. A few decades later, wars with Phoenicians and Celts, combined with inner strife, brought fourth its demise, and the British Isles became dominated by Celtic tribes immigrating from continental Europe, absorbing the Elvish population.
Elves in Celtic Britain
This, however, was not the end of the Elves. A few pockets of Elvendom remained, the greatest and most important being that known in Celtic as Avalon and in Middle Albic as Abhallanda 'Apple-land', centered on the city of Glastambara (Glastonbury). The Old Albic language, however, changed into Middle Albic, a language with a somewhat trimmed-down morphology; the relationship between Old and Middle Albic can be compared to that between Sanskrit and Pali. In these pockets, Elvish culture continued to flourish, but with less splendour than in the old Commonwealth, and became gradually influenced by Celtic culture.
In the year 55 AD, Joesph of Arimathea arrived at Glastambara, bringing with him the teachings of Jesus of Nazareth, and, according to the Gospel of Joseph of Arimathea, also his son, though the existence of the latter has been denounced by most Christian churches and is doubted by most historians. At any rate, this left a lasting mark on Elvish religion. The emphasis of worship shifted away from the Macaveni (who weren't abolished entirely, though, but identified with the Archangels) and towards Éa who was identified with the Judeo-Christian God. The resulting religion, Rosicrucian Christianity, was antitrinitarian: Jesus was not the Son of God and part of a Holy Trinity, but a prophet - a mortal human being who spoke wisdom inspired by God, no more and no less.
The arrival of Roman Catholic Christianity on the British Isles in the 4th century caused tensions between the Roman and Rosicrucian forms of Christianity. In the early 6th century, a coalition of British chieftains, according to tradition led by King Arthur, waged war against the Elves on the ground that they were "wizards and heretics". Avalon was eventually conquered, and no place remained where the Elves could live unmolested. The Elves' reaction on these events was the Hiding: they disappeared from history, effectively becoming a secret society which clandestinely upheld the old Elvish ideals and began plotting for the injection of Elvish ideas and values into mainstream western culture. Many Elves became Moonchildren (Sinjenrin Sinjen), a nation of travelling showmen. The Elves have been in the Hiding ever since then and still are there today.