The Frozen Forest Planet
I should mention, this campaign setting was inspired from two threads in the RP section here, Kobolds vs. Gnomes and what fantasy race you hate. It made me realize that I was particularly alone in liking gnomes and elves, so I decided to play into it.
In the Beginning
The world of Nchi was once your average world much like Greyhawk. Way too many intelligent races for anybody to see half of them. Humans, Elves, Halflings, Dwarves, Orcs, Gnomes, Lizardmen, Goblins, Kobolds, Changelings...... Many of the common stereotypes held true here.
Of particular note is the elves, the embodiment of arrogance, demanding that all other races address them as the superiors they rightfully
were. This caused a rather universal revulsion, to the point where the elven goddess, now known as Elu Kivi, was sealed on the planet by the other deities just because they were sick of her and her elves.
Eventually, the elves got sick of this too, which is where the trouble started.
The Forest Cataclysm
They retreated to the deepest depths of their forests gathering the most powerful elven magic-wielders in the world. Then, in a powerful joint ritual, reshaped the world to put them at the top. All terrain became dense woodland with so tall they practically defy physics. At the site of the ritual was the greatest tree of all, Ilmapuu, or "The World Tree."
Much like the terrain, the species were twisted in the ritual, humans became shifters, kobolds and gnomes twisted to accommodate their new jungle and swampland surroundings. Those dwarves unlucky enough to be on the surface at the time twisted in a way that made them no longer able to survive in subterranean society. The three civilizations living deep underground, the Deep Dwarves, Changelings and Rock Goblins were unaffected, and just decided to seal themselves off from the "surfacers."
For a time, the elves ruled in their rightful
station, if only because they were the ones most able to live in the new environment, and thus needed to be looked to for survival. As soon as survival was no longer an issue, there were many who worked to fight the elves in their own game, practically the entirety of the forest dwarves, and half of the swamp gnomes (as well as sizeable communities of shifters) traveled west, as far from the original cataclysm as possible.
The Frost Cataclysm
This group threw together their own ritual, just as powerful as the previous. World and creature shifted to become at home in a new perpetual arctic terrain, dividing the world East and West in Arctic and Thawed.
The new Snow dwarves promptly dug out the deep dwarves letting them know it was safe to come back out. In current (insane) dwarven king felt it was high time to conquer the world, and about the same time a war broke out between arctic and forest. The deep dwarves eventually broke it up when it stalemated and created a large globe circumnavigating wall dividing the two sides, creating a fort that would serve as the economic center of the world in the new age.