The town of Mill Run came first. The valley was settled and the main crop is grains of various sorts, which explains the fact that the first thing built was a mill on the river. The town grows and the mill owners, the Millibanks, gained influence over the years, eventually gaining a title as well. The build a castle in the hills on the one side of the valley.
After a couple of centuries, a family feud split the Millibanks. One brother retained the family name and castle while the other took his mother’s maiden name, Prethus, and built a castle on the other side of the valley. The families spend the next century or so feuding over the town and the fertile valley. The valley’s fertility is not only from the yearly flooding but from the blood spilled in the many battles.