After all, the Heavens, although having gone through declines and falls hadn't died yet and hadn't returned to Chaos. If Di Tou really tried to borrow the power of the Void in the world, although he wouldn't have weak and strong spots like someone who cultivated or Resonated with the wind or water, he also wouldn't have the sweeping effect and potential of someone who cultivated such a law.
When someone who Resonated with the law of wind fought in a windy gorge, in an instant great winds would stir and it was like the entire world was at their fingertips, striking down with furious gales. But if Di Tou were to try… all he would find was that he was stronger, faster, and more in control of his various senses like his Spiritual Sense.
He could borrow strength from the Heavens, but not the concept of the Void, as although the Void was everywhere, it also wasn't anywhere in the current Heavens.
