From the introduction:
The region known today as Ull was settled by several Oeridian tribes from Western Oerik, seeking to avoid the depredations of war, slavery and humanoid expansion. Their respite was brief however, as the onset of the Baklunish-Suel Wars (-485 CY) threatened stability in the region. The Wars soon escalated with both sides recruiting burgeoning hordes of humanoids for the first time (-466 CY). At the same time these humanoid mercenaries battled one another, they were also turned aside by their purist employers to inevitably begin pillaging north and east into Oeridian villages. Within a decade the pressures of the Wars and unrestrained humanoid incursions finally became too great for many Oerids, who left behind their settlements and resumed their destined migration to the east beyond the Tuflik valley. Not all Oerids would leave so easily though. The stubborn Yorodhi, at the time a rival of the mighty Aerdi tribe, were tired of flight and refused to be driven from their lands.