The relationship between the nine tribes that had once served Emperor Kua was a rather rocky one. Even though they worked together, they were also rivals.
They had all served Emperor Kua before. When the emperor perished, the nine tribes remained separate entities, competing against each other for many years. They all wanted to become the true successors of Emperor Kua and inherit the will of the emperor. Doing so would allow them to unify all nine tribes.
If one among the nine reached the Renhuang Plane, everything would naturally come to a close.
The so-called Renhuang ruins were the ancestral lands of the nine tribes. They had been trying to inherit whatever was left behind by Emperor Kua for many years.