The great war occurred nearly 200 years ago, and broke what was once a cohesive continent into several different states.
The war began when a group of humans made a pact with devils, turning them into Tieflings. They founded a great empire near Arkhosia in what is now known as the Free Lands, but their reign of terror was not tolerated for long. The Dragonborn nation of Arkhosia were the first to wage war on the devils.
The war went badly for the Dragonborn, their nation conquered city by city, until a Dragonborn Hunter named Faridian brought the lands to the east of the Eofel Mountains as reinforcements, then known as the Chandroosan.
The fighting lasted for nearly fifty years, and when the dust had settled the Tieflings had been driven from the shores of Errastus to lands unknown across the sea. Arkhosia lay ruined, and the Dragonborn people to few to properly rebuild and reclaim their lands. Humans were mistrusted by the other races, for it was they who gave rise to the Tieflings. Many humans traveled to Ricarnan, and the Human Empire was born.