The reason they cared so much about the Hongmeng Crystal was that it represented future possibilities.
Soul's original plan had been to provoke a conflict and end the journey. Through Loneliness's words and actions, he had already calculated and teased out the Hongmeng Crystal's location. If he could drive the others away, he would have a chance to claim it all for himself.
To explain why the Hongmeng Crystal was so important, one had to start here.
One had to explain the structure of the world they inhabited.
The Ancient God World was the name they had given their own world after first entering the Chaos Sea and seeing countless Great Thousand Worlds. They had each used their powers to leave marks upon their world, lest people from other worlds suddenly intrude.
Normally, that was impossible, but their world possessed an extraordinary distinction: the Ancestors who had created it were still alive.
Moreover, those Ancestors had led them in conquering another Great Thousand World.
They called this powerful being the Ancient God.
Their relationship with the Ancient God was also very simple. The Ancient God was their father.
Yes, the living beings of this world were the Ancient God's children. Each had inherited a portion of his bloodline and learned some of the rules he commanded.
From birth, their strength was destined to reach the realm of a limitless primordial Daluo golden immortal.
In their own system, however, this level of strength was called an Ancestor.
Having explained the Ancestors, it was time to mention their respective Divine Races.
Their relationship was the same as that between the Ancestors and the Ancient God.
These Divine Races had all been created by them, each inheriting their divine power.
Cultivation did not exist in their world, for they were gods, and their