Naturally, the people of the immortal sect wanted to convince them to enter the sect, but since words of kindness alone had failed to convince them to obey and worship the sect, they considered using strength to suppress Xuanyuan Mo Ze and Feng Jiu and prove to them that outside of sky there is the sky, outside of people there are people. Even though they were powerful, they were not as strong as the immortal sect's Venerables.
The immortal sect's reputation would be harmed if they were not subdued, so they suppressed them at every turn and urged them to take the two Venerables' challenge.
However, the challenge was unfair. Xuanyuan Mo Ze had the ability to defeat the earlier Venerable, but he might not be able to win against Venerable Si Que. What's more, even if he had a slight chance of winning, Feng Jiu might not be able to defeat Senior Brother Mu Xin due to her diminutive frame. It should be noted that these two were the two most powerful Venerables of their generation.
