So, I was thinking about Beastmen and Demi-humans. If you elevate beastmen to demi-human status, then it seems weird to have, you know, hyena-men, lizard-men, bear-men, and.... short men. It just seems more coherent if elves and dwarves are beastmen too.
So, elves are bird-men, and dwarves are badger-men. You've got your shifty thief-broker Raven-Elves, your mysterious and terrifying Owl-Elves, your gregarious Parrot-Elves...
So what makes beastmen? Lots of things! Sometimes it's the natural byproduct of generations of living in a particular high-mana area. Sometimes gods take it upon themselves to 'improve' the locals, molding them into a preferred shape. Sometimes it's a deliberate act by humans in an attempt to improve themselves.
The bear-men of the North are bears that an ice-god granted intelligence and thumbs.
The centaurs are self-made, having used magic to fuse themselves with horses for obvious reasons.
The ogres are naturally occuring- they soaked up the strength and vigor of their volcanic homeland.
The toadmen were created by the ogres as servants.
The lizardmen were rewarded by their swamp-gods.
Nobody is 100% sure about gnolls. Some postulate that a bored god decided to create a violent, chaotic race for their own amusement. Others believe that their manic intensity marks them as having been twisted by the firey mana of the desert itself.
Dwarves and Elves I haven't decided yet, and welcome suggestions.