Xu Nian naturally didn't have the ability to remove the Extreme Cold Viper Poison that even a Nine-star War Sect couldn't resolve, but just because he couldn't remove the poison didn't mean that Emperor Ye Tian couldn't.
Such poison was, for Emperor Ye Tian, virtually effortless to eliminate.
As for helping Yan Wu break through to the Xuantian-level Battle General realm, it was because Yan Wu had long reached the bottleneck of the Nine-star War Sect. However, he had always been depleting a considerable amount of strength to suppress the Extreme Cold Viper Poison, which prevented his breakthrough.
Once he was helped to resolve the Extreme Cold Viper Poison, his breakthrough to the Battle General Level would naturally become a matter of course.
"Sit cross-legged now, channel your Combat Technique, and I will help you with the poison," Xu Nian instructed Yan Wu.
