Beastkin

Beastkin are the most internally diverse of all subspecies of Mankind (and, in fact, the most internally diverse species out there). They have hundreds of subspecies, although this number is typically lowered down to few dozen 'effective' subspecies. It is achieved by (for example) contracting all cat-derived or wolf-derived subspecies into single subspecies (essentially demoting the remaning differences into 'races' within a subspecies).
On the most basic level they are best described as hybrids (mental and physical) of humans and select animal species. They are upright humanoids with a varied degree mix of human and animal bodily components, who are mentally human-like - but also with certain degreee of 'animalistic' instincts. The situation is rendered much more complicated with the biological schism of beastkin, with various cosmological regions of the worlds having beastkin with different way of mixing their human and non-human parts.

Basic Information

Anatomy

There are several variants of the beastkin, each version belonging to different cosmology. Each of them has different ratio of human to animal features (in body and mind). This have nothing to do with their genes, as two beastkin of the same variant that will move to another cosmology and have children there, will have those children be of the local variant of their species.
Those variants are as follows:
Menorian Beastkin who are currently considered extinct in the cataclysm that destroyed Menoria. This original species of the beastkin is believed to have been nearly entirely animal in their looks, but with a fully human intellect and ability to speak human language. In fact, no one is fully certain if they truly classified as a subspecies of humans back then.
Umbral Beastkin who are considered by many to be the original variant, which is not true. They are upright and anthropomorphic animals, with nearly no human traits aside from an upright position and opposable thumbs, with the least intelligent of them barely counting as sapient. They are almost entirely ruled by animalistic instincts and are incredibly aggressive.
They are primarily encountered on parts of Telya held by the Umbral Bond and in the Ice Kingdoms, which is a holdout of Umbral Bond in Karadia.
Karadian Beastkin who are a middle-step between the Umbral and Khardic beastkin. They are upright standing humanoid with a relatively high degree of animal features, including the ears, eyes and tails, with often enhanced claws and teeth. The beastkin of the animals with furs, scales or feathers have those features cover majority of their body, usually only with an exception of chest, abdomen, genitals and faces, though hands and feet are usually also largely human.
They do possess certain degree of animalistic tendencies and quirks in their behaviour, and are often rather ferocious in combat.
Khardic Beastkin were created as a result of the birth of the World Symphony, which began to reform the Telyan Beastkin into their own version. They are the most human out of them all, usually only possessing ears and tails of their animals, with their body being almost entirely human other than that.
They appear to be capable of a full spectrum of behaviours, both entirely human and entirely animalistic, depending entirely on their own choices and lifestyles.
Eastern Beastkin are a complicated issue, as no one is fully sure if they truly are beastkin. However, visitors to both the Ind subcontinent and Nippon reported encountering a variety of human-animal hybrids, often rather diverse in their looks. However, due to the status of those lands as the Lost Lands, it is unknown if they are mortals or spirits.

Biological Traits

Subspecies

Due to simple number of subspecies, only some of the most-common ones will be mentioned. The rest will be-added on a strict need-to basis. Majority of them are mammal-derived (likely due to such animals being the most compatible with humans), thought there are cases of reptire-derivatives, amphibian-derivatives, avian-derivatives and even some hybrids with the creatures of the seas.
However, most of those other subspecies suffers from some structural issues. This is believed to be the result of an imperfect work of the overlords of the Umbral Bond, as it is believed that the other animals were massively more popular among the now-extinct Menorian Beastkin, but are very rare among the Umbral Beastkin and their descendants.
The examples of those subspecies are as follows (listed alphabetically):
Bearkin - Tall, bulky, superhumanly strong and with tendency for not liking to listen to anyone else. Bearkin are a terrible sight to behold on the battlefield. They also have good eyesight (in combination with equally good hearing and a sense of smell), resulting in lack of common weaknesses of beastkin. As a result, they are quite common as unstoppable beastkin juggernauts or leader of warbands (typically achieved through an indiscriminate massacre of prior leader and those that remained loyal to him over their successor).
Boarkin - Strong and durable, with a tendency for communal behaviours and being extremely stubborn, and much easier to feed than a lot of other beastkins due to being omnivores that are known to eat almost everything for as long as it's edible. As a result, while the boarkins are often considered something of an auxiliary combat subspecies, often used to form separate formations of melee combatants.
Catkin - One of the two most common carnivorous subspecies of beastkin, known for making up (together with the wolfkin) for majority of the beastkin armies. Catkin are, in an essence, human-cat hybrids. They have a tendency for being lazy and a bit self-serving, and have good motion perception and nightvision, but are shortsighted as a rule, and perceive colours differently than humans. They excel at acting as skirmishers and ambushers, at least partially due to their individualism combined with creativity and higher intellect. They are known to have a notable surplus of females over males.
Cowkin - A herbivore subspecies of the beastkin, that is often seen as a major part of their civilian population. They are fairly strong if usually rather docile, are primarily herbivorous (which allows their society to keep more of their meat for the carnivorous subspecies that form the basis of their military). Their females tend to be rather gifted in terms of their assets and are known to lactate rather profusely. A lot of the civilized cowkins take advantage of that, finding job as wet nurses.
Foxkin - One of the relatively common and successful omnivore beast morphs, foxes are known for their high intellect, and certain degree of manipulative behaviour (they aren't necessarily evil or self-serving on that field, but will as a rule prefer to achieve their goals without getting their hands dirty). As a result they tend to form significant part of the beastkin mages and shamans, and even among the civilized beastkin they will disproportionately often go for 'white collar' jobs, being especially overrepresent among magic users and scholars.
Lionkin - Although the more proper term would be 'largecatkin'. Lionkin (and even rarer in Karadia tigerkins, pantherkins etc.) are essentially catkin, but with much greater physical strength. Their much more pronounced individualism makes them common as leaders (or elite units) of beastkin armies. Even among their civilized kin, they often occupy positions in military and governments.
Lizardkin - A somewhat rare case of a non-mammal beast morphs that has managed to retain a significant population and their own niche within the beastkin societies. Lizardkins have incredible eyesight that's really hard to fool (due to seeing a wider colour spectrum than that of humans), which makes them good scouts and pretty good archers.
Rabbitkin - A somewhat unfortunate beastkin subspecies, that is known mostly for their tendency for shyness and submissive behaviour and their fertility (and, by association, their libido). They can be surprisingly ferocious when cornered, but this is far from being enough to warrant them any sensible position in beastkin societies. They are often seen as concubines for various beastkin warlords. If not for the Grand Empire not liking the concept of species-based slavery, most of them would probably be openly traded around.
Sheepkin - A common case of beastkin civilians, known for being fairly docile (like most of the herbivorous beastkins) and for the fact that they actually produce some amount of wool that's often used to produce usable textiles by the beastkin. They lack other notable traits.
Wolfkin - One of the two most common carnivorous subspecies of beastkin, known for making up (together with the catkin) for majority of the beastkin armies. Wolfkin are, in an essence, human-wolf hybrids (although many larger dogkin breeds are functionally counted as wolfkin). They are disciplined and tend to operate in packs. Have similar problems with eyesight as the catkin (so partial color-blindness and shortsightedness). They are good warriors, even if rarely turn out as warlords of beastkin armies.

Genetics and Reproduction

Relatively close to human baseline, however just like the perception it varies slightly depending on the animal half in question - for example beastkin of litter-bearing animals will have a tendency for a surplus chance of multiple pregnancies. There will also be variations on the field of, for example, pregnancy length. Like in the case of other biological traits, the beastkin are typically somewhere between pure humans and 'their' animals.
One thing that's common to all beastkin is the fact that their trait inheritance works on two levels. Each of them is a result of animal half partially 'overwriting' their human part during the gestation. Their genetics are almost entirely identical to baseline humans, and their animal side isn't coded in genes. Instead it acts as more of a hereditary curse (or blessing). The brand of the curse is typically aligned with gender, so for example a catkin father and wolfkin mother will result in catkin sons and wolfkin daughters, with their animal-side superimposed onto a baseline human form (with its details governed by baseline human genetics and inheritance).
They can have children with other humans and a select other species that can interbred with baseline humans. Their curse/blessing is tied with gender too, so for example a baseline human man paired with a catkin female will have human sons and catkin daughters.

Dietary Needs and Habits

Varied, from purely carnivorous subspecies (a massive drain on their maximum population, making them offer appear as dedicated warrior caste living off their herbivorous cousins) to ones purely herbivorous.

Additional Information

Perception and Sensory Capabilities

Greatly varied on every possible level between the subspecies. This is considered to be both their greatest strength and greatest weakness - depending on the animal they have the features of, they can have senses far above the human baseline - or far beneath it. This is much less pronounced among the khardic beastkin, who are the most human of them all.
In some cases, however, the khardics are superior to other subspecies - cat-morph khardic beastkin will have the improved hearing of a cat but would lack the natural short-sightedness and weakened colour palette due to having fundamentally human eyes.

Subspecies

Carnivores

Bearkin
Catkin
Foxkin
Lionkin
Wolfkin

Herbivores

Cowkin
Rabbitkin
Sheepkin

Omnivores

Boarkin
Lizardkin