Two great human empires use to sit in the western portion of the Flanaess. All that is left now is a sprawling desert. The Baklunish and Suloise empires were the pinnacle of human achievement, but they thirsted for the blood of each other. By using dark, soul-wrenching magics, they wiped each other from the face of the Oerth. After this devastation, there was a mass immigration of humans to the east and across the Flanaess.
The demihuman inhabitants of the Flanaess were pushed back as the humans came flooding in. Once the humans had a grip on the western Flanaess, they began expanding exponentially, overtaking elven cities and dwarven strongholds alike. This completely shifted the power in the Flanaess, and within a few generations, humans were the overwhelming majority on the continent.