"Li Xiao..." Tu Lishan signaled Li Xiao to attack the outer wall of the fortress in front of them.
Li Xiao struck with his palm, a roaring Gang Qi like cannon fire crashed fiercely onto it.
However, the outer wall didn't budge an inch, and instead, Li Xiao felt a strong rebound force, causing him to step back several paces, looking at the fortress's outer wall in astonishment.
Li Xiao exclaimed, "After so many hits, it's still this sturdy? What kind of material is this?"
"This is Zhang Yu's digest." Tu Lishan pointed to the entire fortress ahead and sighed, "Most of the building materials for this entire fortress are his digest."
With that, he pointed out a small piece of uneven texture on the inside of the wall and said, "Look, these are Zhang Yu's stomach patterns, the marks left from the violent compression of the stomach during material processing, his digestion marks."
