It's not to say that Pei Xuanjing's existence influences the pattern between heaven and earth, but Pei Xuanjing can only guarantee a relative fairness, not absolute fairness, only that there are some opportunities, but not that every cultivator will be treated exactly the same.
The gap between cultivators of the top immortal sects and those of ordinary immortal sects, small sects, and independent practitioners is inevitable, a necessary scene on the path of many a True Immortal's cultivation.
Initially, they thought everything could change after certifying as a True Immortal, but after achieving that, they discovered that even as True Immortals, those from top immortal sects were still beyond their comparison.
If you take advantage of me before I certify as a True Immortal, and you still take advantage of me after, then what was the point of my ascension?
