As fourteen attacks struck the sealing barrier, ripples suddenly spread outward from each point of impact. The entire barrier rose and fell as if it were made of water, leaving even Nine Kills inside the space somewhat unsteady on his feet.
"How is that possible?!" Nine Kills stared at Shi Feng in disbelief.
Previously, Shi Feng had been allowed to attack the barrier as much as he wanted, yet it had not reacted in the slightest. Now, merely increasing the number of attacks was enough to produce an effect?
"Could it be...?"
All of a sudden, Nine Kills thought of a possibility.
Stacking force!
It sounded simple, but it was exceptionally difficult in practice. One had to strike the exact same spot at the exact same time. Such precise control was not something an ordinary expert could achieve.
Of course, for an expert like Shi Feng, combining two forces into one was not a problem. However, merging three or more forces together was far more difficult.
It was like how some people could multitask between two things, but handling three things at once increased the difficulty geometrically.
Still, it was not as though there was no way to learn it. It was simply that such methods were never passed around casually, and only a very small number of extremely close people could possibly learn them.
Thinking of this, Nine Kills could not help heaving a sigh of relief.
Shi Feng's strength was indeed formidable, but relying on the stacking of two forces to reach Tier 4 standards was still far from enough.
Even with Shi Feng's current strength, it would be impossible without merging at least three or four forces. Yet trying to control the fusion of three or four forces without having learned the method was nothing but a