The shadow hardly had time to be shocked that Theron actually dared to attack him when the first blade appeared before his eyes.
There wasn't enough room to maneuver in the cave. They hadn't had much time to form the tunnels in the first place, so the width was only about three meters or so. As for the lengths, there were many twists and turns in order to form the formation that filtered and controlled the sound.
Due to that, there wasn't even remotely enough room for the shadow to take advantage of his speed. By comparison, Theron's ability to accelerate, decelerate, and change directions was actually far superior.
His body was truly akin to fluid water. He crossed the handful of meters that separated them in the blink of an eye, slashing down with strong might.
The flash of blue forced the shadow to dodge. There was simply no way he would dare to take that blade head on again, not without a weapon that could match it.