Elfwars

In a few hundred years Elves went from a magical curiousity to the dominate force on a continent. The Grey Order and Megalos reacted poorly. Fear lead to a campaign to wipe out the Elves. This led to more than a hundred years of bloody warfare.
It was the most brutal warfare ever seen. The Grey Order summoned and created horrible creatures to slaughter the Elves. Megalos declared a holy crusade. Many died and the Elves were pushed northwards back to the highlands.
As Megalos and the Grey Order managed to take ground, they also incurred more problems. In the highlands lived the oldest of the Elves and the logistics of waging a war so far away began to take its toll.
In desparation, the Grey Order and Megalos started augmenting their forces with the Orcs. Seemingly subserviant brutes, Orcs were summoned in large hunting parties. These hunting parties were then unleashed to hunt and kill in Elvin territories.
In the beginning this worked very well, but then the Orcs began to multiply. In small hunting parties Orcs deferred to the more powerful forces of the Grey Order and Megalos. In hordes they didn't. Shortly, both nations had a new and more dangerous problem to deal with.
At first the Orc problem seemed to be confined to the Elvin continent, then war parties started appearing within the Grey Order and Megalos. True to form, the Orcs slaughtered human settlements they could easily overpower just as they had been doing on the Elvin continent while avoiding forces they could not beat. Fearing the war parties would unite into a horde on the mainland, both the Grey Order and Megalos withdrew their forces from the Elvin continent.
The withdrawl of the nations allowed the Elves to focus on the Orc horde. Unlike Megalos and the Grey Order, Elves had spent years studying and killing the Orcs. Using guile and trickery, the Orcs were quickly cleansed from their land.
On the mainland, Megalos managed to purge their Orc infestation but the Grey Order did not fare as well. By using an impressive display of magic, the Grey Order managed to push the growing Orc hordes westward into some human tribes. The Orcs slaughtered and enslaves the native humans while carving out a nation of their own.
Having dealt with the Orc threat, the Grey Order and Megalos found themselves back where they started. The Elves had managed to reclaim their continent and replenish much of their population. Rather than start another war, a treaty was signed. This treaty was called the "Branch of Life" and prohibited the Elves from expanding to the mainland.