They didn't know what origins Ye Lanfeng had, but since he was Han Yan's servant, no matter how high his strength could be estimated, it shouldn't be too high. If facing other opponents, they might manage to fight with effort, but when confronting Tributor Qiu who cultivates the Domineering Body Technique, there's simply no way to attack. The heavier the blow, the greater the injury.
Only then did Han Yan understand why Tributor Qiu was so fearless. She had also heard about the power of the Domineering Body Technique; unless one's strength was far above Qiu's, facing his Domineering Body Technique was like a tiger trying to bite a turtle, completely helpless.
If she herself were to fight, it wouldn't be easy at all, she'd have to use her wits before taking action. But since it's Ye Lanfeng who's acting, Lady Mu has no need to use her brain and isn't worried at all.
