That secret to breaking through to the Heaven Opening Realm, exchanged for military merits, should have been this.
The so-called Earth Water Fire Wind did not necessarily mean Subordinate Rules from the four Main Rules of Earth Water Fire Wind. Any four Subordinate Rules possessing the characteristics of Earth Water Fire Wind would suffice.
This secret to breaking through to the Heaven Opening Realm was, in truth, merely a layer of window paper.
For those who did not know it and wanted to figure it out themselves, it was exceedingly difficult to guess. After all, how could one verify it? That alone was an enormous problem.
Among the Human Emperor Venerable inheritances Chen Fei had seen, there had been countless ideas on how to break through to the Heaven Opening Realm, yet none had ultimately been able to prove whether those ideas were true or false.
Mastering a Main Rule to break through into the Heaven Opening Realm was actually the most common conjecture in the human race's inheritances, but it was also almost the least achievable path.
In the Black Stone Domain, mastering two Subordinate Rules already made one an exceptionally powerful Peak Dao Integration Realm cultivator.
Throughout the long history of the human race, Emperor Venerables who had mastered three Subordinate Rules were as rare as phoenix feathers and qilin horns. Moreover, those three Subordinate Rules had all belonged to branches of different Main Rules.
Among Subordinate Rules under the same Main Rule, the most any Human Emperor Venerable had mastered was two. When it came to a Subordinate Rule under a third Main Rule, they simply could not continue.
Comprehending them was especially difficult, as though Subordinate Rules beneath the same Main Rule repelled one another.
Choosing and mastering four Subordinate Rules similar to Earth Water Fire