An avian, more often referred to colloquially as a birdman, is a humanoid being taking the appearance of a feather-covered man, with the wings and head of a bird, and talons instead of hands. Avian is in actuality a blanket term for a myriad of different subspecies of birdmen, but given that most of the less stout breeds have long since been forced to extinction, the term is most often associated with the Buteon, which share resemblance with eagles specifically. In the modern age, avians live almost exclusively in the Eyr Mounts in the northernmost reaches of Engelain, and are known for their technological feats, altruistic nature and lack of emotional depth.
In Avianic lore, the birth of the avians predates that of mankind. They do not believe that they were involved in the creation of the world via Tyrrus, and in fact actively deny such a claim. Instead, the avians believe that the world is timeless and has always existed, needing no creator for it is existence personified. Their ancestral god they name Sarcoseth, who came to the Eyr Mounts and roosted there, and from His eggs hatched the avians. Sarcoseth then departed for other worlds, to roost in all of the realms in existence and spread his children. In this way, all avians are quasi-gods, and ancestral worship is a common religious component within the avian community, as further generations are further diluted from the true blood of Sarcoseth their Father-God.
The avians do not seem to hold any belief for how any other creature came to be- nor do they seem to care. Some believe that regular birds are descendants of Sarcoseth as well, though others are dubious of this. The avians seem to accept the existence of Tyrrus and attribute him with creating mankind, but they see Tyrrus as a young god, and inconsequential to their own lifestyle. Religion in avianic culture has begun to witness a steep decline, as many believe the blood is too far diluted now for them to be considered holy children, and most agree that Sarcoseth is set never to return. As such, avians are highly atheistic as a whole, in stark contrast with most other beings that live within Engelain.
Sometime after the Fall of Annwyfn at the hands of the Defiler of the Old World, the avians began a massive project- to hollow out the mountains they call their homes in order to harness the fiery power of the earth. In this effort they began the mass enslavement of the dwarven race, who were forced to toil down in the mines for centuries until the forges of the birdmen were complete. After their great work was done, the avians released the dwarves and have not indulged in slavery since- though the dwarven race holds a deep-seated hatred for their apathetic former masters.
As mentioned earlier, 'avian' is simply a blanket term for many different subspecies of birdmen. There is somewhat of a caste system, perhaps determined by size and strength though backed up religiously by lifespan- those that live for longer have had fewer generations pass between them and the firstborn of Sarcoseth, and are therefore more righteous than those with a shorter lifespan. It is believed that this rigid caste system is what caused the great rift which lead to a civil war in the Eyr Mounts, eventually leading the avians to separate into two distinct groups.
The losers of the civil war were what came to be known as the grassland avians, the weaker cousins who fled the mountains to make their own home. These were the duckmen and the turkeymen, the robinmen and the pigeonmen, all of the more feeble kinds of birdmen. They headed southwards into the Great Plains, and eventually came to settle for the most part in Southern Engelain above Tywrought. They had at the very least a rudimentary culture, and held dealings with the centaurs and the satyrs that also occupied that region. However, when the Tyrannian Empire came to be and started its expansionist era, the grassland avians would come to blows and eventually be driven to extinction by the Empire.
This left behind the strongest of the avians, that were once called the mountainous avians though now the term is defunct- they are the only avians left. They are made up almost entirely of the Eaglemen, strongest and smartest of their kind. With their great work under the mountains complete, the avians no longer needed to travel south for the winter, and turned their eyes to scientific discovery- the avians are by far the most advanced species in Engelain, building steam-powered engines and using the warmth of the magma which surrounds them to power their many and myriad machines.