Fox spirit's advantage relies mainly on the energy they store in their tails. Therefore, the existence of something that could make him, a nine-tailed celestial fox spirit, lose quite an ample amount of mana for a short time is a threat to him.
That is what Shen Yuan had in mind when he said he found his weakness. However, his three agents have different ideas.
"Hmm!" Li An nodded while sporting a thoughtful expression. "I also find it baffling. How could that dagger easily penetrate a cloth made from Steel Silk Arachne? And not just that, who is capable enough to throw a weapon undetected by someone exceptionally sharp like Leader Shen?"
Hu Feng and Wen Huian bobbed their head to express that their thoughts were the same.
The celestial fox spirit sighed. Their understanding is off by ten points, but he must admit, their questions also hit the home run.