It's just as easy to lump the animal hybrid folk into one category as it is with every other race. Generally Beastmen follow instincts more than rational thought, there skin is at least partully covered in something other than human skin depending on there mix (scales, fur etc). They'll generally have at least one characteristic that matches there mix such as claws, a tail, that sort of thing.
Every other race is just as diverse they just generally conform to a humanoid appearance. The southern elves are most likely completely different from the Northern Elves of Reach that we've learned about thus far. There are hundreds of different kinds of humans, black, Latina, white, Asian the list goes on. We still call them human.
That point aside unless it was some very specific magic administered over enough time that they would know what was happening then this sort of thing had to be caused by demonic magic. However twisted the demons are they don't do things without a reason. Most of the time the things they do are for food or enjoyment. There is no reason why they'd give a set of warriors more powerful bodies without proceeding to slaughter them very slowly and painfully afterwards. This transformation more or less allowed the warriors to take control of a good portion of the country side. Demons don't give out that kind of power for no reason.
Every other race is just as diverse they just generally conform to a humanoid appearance. The southern elves are most likely completely different from the Northern Elves of Reach that we've learned about thus far. There are hundreds of different kinds of humans, black, Latina, white, Asian the list goes on. We still call them human.
That point aside unless it was some very specific magic administered over enough time that they would know what was happening then this sort of thing had to be caused by demonic magic. However twisted the demons are they don't do things without a reason. Most of the time the things they do are for food or enjoyment. There is no reason why they'd give a set of warriors more powerful bodies without proceeding to slaughter them very slowly and painfully afterwards. This transformation more or less allowed the warriors to take control of a good portion of the country side. Demons don't give out that kind of power for no reason.