Heralds of the Crescent Moon
The Elves are the eldest and longest lived of the races. They are also fairly isolationist. They rarely leave their cities, preferring to deal only with their own kind. They will send out trade delegations to deal with both Humanity and the Dwarves on occasions, and their good are coveted and expensive.
Centuries ago, Elves had enslaved Humanity for ‘their own good’. Elves had progressed at a much rapider rate. They were civilized while Humans were still living in huts and tiny villages. The Elves took Humans into their homes to civilize them. At first it was a very kind and humane thing to do, but eventually they became subservient creatures. After centuries of enslavement, there was a revolt. A long war for freedom took place. The Elves expected to win easily, but they underestimated the human spirit. Humanity eventually won.
For years tensions between the two races were strained. Humanity took much of what they learned from the Elves, and created their own nation. This nation eventually split and became the four Kingdoms. As the Elves retreated more and more into their own society, entire generations of humans would come and go without ever seeing an Elf. Eventually, the old hatreds died away.