The Southern Border Witch Kings' attitude towards Lu Country over generations alternates between enmity and submission. The first generation was hostile, the second submissive, the third hostile again, and the fourth submissive once more.
In summary, they flip-flop between defiance and obedience.
With the benefit of hindsight, the Lu Country Privy Council was naturally cautious about the Witch King's submission. Was their allegiance genuine? It was more likely due to the five Golden Core True Men forcing them into submission.
However, on his first day in Pingjing, the new Witch King, Hu Minghua, proposed a significant treaty:
Southern Border would cede land.
In simple terms, all the major Sorcerer Lords of the Southern Border wrote a joint letter, delivered by the new Witch King, hoping that their dominions could join Lu Country as autonomous regions.
