The Onocentaur were a race native to Engelain, more specifically the Great Plains, and a close cousin to the centaurs. They had the torso, arms and head of a human, but the hind quarters of a donkey. Though physically weaker than the centaurs and aesthetically less appealing, (their females were supposedly quite as hairy as the men, perhaps making them half dwarf rather than half man,) the onocentaur dwarfed their loftier cousins when it came to craftsmanship.
Historically they are very seldom mentioned, being originally a race of little significance. They came to prominence after the centaurs moved to take over the entirety of the Great Plains some millennia ago. The onocentaur differed greatly from their cousins in two main ways: they were innovators, believing in constantly progressing rather than keeping to their conservative values. And they were also settlers, wishing to shun the nomadic lifestyle that the centaurs had taken on. Thus the onocentaur were pioneers in the symbiosis between advancement and beauty, erecting great cities made of glass, where light of a thousand shades danced through the streets, where the sound of rainfall made a beautiful harmony, where the night sky would be reflected downwards and surround them.
Though the cities of the onocentaur were widely regarded as one of the great wonders of the world, making them of glass had one vital mistake: they were easily shattered. When the Tyrannian Empire advanced northwards into the Great Plains, the onocentaur were hopelessly outmatched, the resultant wars leading not only to the destruction of their city of light, but also to the eventual extinction of the onocentaur. This event is often regarded as one of the great tragedies in history, and may be part of the reason why centaurs are so haughty when it comes to interacting with mankind.
It is unknown if the onocentaur worshipped the Great Stallion like the centaurs do, for the onocentaur kept no written records, instead passing down vital information through song and poem, and there is not a being left alive today that know how to sing the old songs.