There was an unwritten rule in the Abyss World. More accurately, it was a rule formed based on common practice.
Pure-bloods were nobler than mixed-bloods.
In the dark apparition race, bloodline was the deciding factor. One's birth, talent, and status were all based on one's bloodline.
To the pure-bloods, mixed-bloods were lowly slaves, like the bugs in the mud. They could order them around however they wanted.
As long as they didn't reach the general stage, the mixed-bloods must always bow to the pure-bloods.
Many pure-bloods kept mixed-bloods as their food and slaves.
The mixed-bloods couldn't get resources, so they were unable to reach the general stage. They could only remain inferior to the pure-bloods and be their slaves.
It was an unfair world for the mixed-bloods.
This was why the four dark apparitions became so conceited when they saw Wang Teng and Zi Ye's appearance.