Centaur History
One of the most truly unusual races in the world, Centaurs are biological hybrids of hominid upper bodies and horse-like lower bodies. They are the only officially recognised Fairy species to lack access to magic, but they more than make up for it with sheer intelligence, with many of the greatest minds in history being Centaurs. They also have the lengthy lifespans that other Fairy races enjoy, despite their lack of magic. The exact cause of this remains unknown.
The origins of the Centaur race are shrouded in mystery, even to them. The Centaurs of the Hellenic Peninsula were the first to develop a written language, albeit a very complicated and jealously guarded one, with the specific intent of recording their history no less, but even their oldest surviving records shed no light on just how they came about. One thing is abundantly clear, however, and that's the fact that Centaurs did not evolve naturally.
The most commonly accepted theory is that, many millennia ago, a group of magically-gifted people (whether they were Fairy, Human, or even a common ancestor is hotly debated) began to experiment with body modification arts, reconstructing themselves to excel in certain fields. Eventually, their skills coincided with a need to become nomadic, and over a relatively short period of time this group transformed themselves to become the union of speed, strength, and intelligence through the introduction of equine bodies.
Studies of Centaur genetic records indicate that ancient horse DNA is indeed present in their very core. However, they are not quite as beefy as the classical stories would have you believe, certainly not like the muscle-bound warrior-poets of Greek myth. Ancient horses were rather smaller than the mighty beasts of burden we know today, a fact that is reflected in the less-than-overwhelming size of the modern Centaur. As such, they can (with some effort) fit in just fine in the living spaces of other Fairies. This relatively small size did not stop the Centaurs of old from having fighters of their own. Typically favouring pole-arms and bows, they were known to fight in a highly mobile manner, always keeping their foes at a distance and retreating at high speed when necessary. Their tactical acumen was well sought-after by the old Fairy Kings and Lords, and Centaurs were frequently seen in the higher ranks of their armies... though rarely on the frontlines.
In the modern era, Centaurs have become quite uncommon. The reasons for this are debated, but not in polite company, and certainly not amongst the Centaurs themselves. Some posit that, given they are adapted to live in wide-open spaces, the underground nature of Fairy civilisation is just putting a dampener on them. Others go so far as to claim that Centaurs have become so obsessed with their intellectual works that they have... 'forgotten' to get hitched, as it were. Another theory is simple: Centaurs have inherited equine skittishness, and are liable to develop social anxiety as a result. It is likely that all these theories have some kernels of truth to them.
The Centaurs are said to have once had a cousin race in Unicorns. However, there is something truly strange here: while the classical image of a Unicorn is that of a white horse with a magic-imbued horn growing from its head, said to be able to grant wishes, no Fairy records actually contain official documentation of their appearance. The race was notoriously shy and few in number, of course, but to evade documentation from their Fairy counterparts altogether is just odd. It is possible that they had access to memory-altering magic akin to modern mind-wiping technology, being so paranoid that they did not even trust their own fellow Fairies.
This lack of actual primary sources on the nature of Unicorns has led them to take on a mythological status in Fairy society, not unlike the one they have in the Human world. They are believed to be extinct, with Human predation for their horns being to blame, but there has actually been debate about whether the Unicorns ever existed in the first place. One theory as to their appearance is rather different from the generally accepted image: they actually were near-identical to Centaurs themselves, save for the horn from their foreheads. Admittedly, this does sound more likely than a race choosing to fully take on the equine form and thus losing access to hands, which are of course the greatest advantage of the hominid races.
In similar fashion, there are theories regarding the existence of the Pegasus people, who had apparently grafted magically-powered wings to their bodies in order to achieve flight, similar to those of Sprites. Even less evidence exists of these Pegasi than there does of Unicorns, and nobody but the more conspiratorially-minded takes the possibility of their existence seriously.