The Beastly Torment

During the fall of the Imperial Colonies and the wars that followed them, many slaves, primarily what Old Imperial Culture considered Beastfolk, escaped their captivity. They roamed the landscape as nomadic, raiding warbands. The local garrison was often either unable to face these warbands or were afraid that if they left their settlements, another warband would attack it in their absence. So the city folk and their local garrison would stay put in their walled settlements while the warbands raided and raised the surrounding villages.
This caused a great famine in the south of Ferra centred around the Flarian Plains and many of these original settlements in the south shrank considerably from the death and destruction caused during the Beastly Torment.
Throughout the Beastly Torment, local, provincial and national governments pushed to contain the crisis. At first large armies were marched across the land but this was both expensive and ineffective as the smaller more nimble warbands would just avoid the great armies. When the armies were split up to chase warbands down or corner them, the smaller sections suffered unsustainable losses against the by now quite experienced warbands.
Eventually, many villages were abandoned and consolidated into small forts. During planting and harvesting season, large groups of soldiers were called up to protect the villages. In some places priests or mages enchanted to crop to be resistant to fire or simply to conjure great storms and rain.
Eventually the warbands ran out of easily raidable villages and suffered considerable losses whenever they attacked the village forts or cities. Hungry and exhausted, the warbands fled through the Highlands Corridor into the Highlands. Here, some would settle while others became nomadic or semi-nomadic tribes. While the Beastly Torment came to an end, raids from the Highlands, while less frequent and severe, would never truly end and especially during times of crisis and war, the Beastfolk would flood into the lowlands again.