As to why he needed to withdraw...
Of course he had to withdraw!
The situation was already crystal clear.
Xu Ling's legacy was of great importance, and within a century, there would inevitably be major changes in this world.
Now, beyond the boundaries of the Void Spirit Realm, a multitude of powers converged, all covetously eyeing this treasure.
The commotion he had caused was big enough. If he did not withdraw now and continued to let things develop, when the Void Spirit Cave Heaven opened in a hundred years, he, the Stone Spell King of Green Jade Mountain who had ruled Liang Country for many years, would inevitably become the primary target for everyone.
This was clearly not what Xu Yang wanted.
So he chose to withdraw after achieving his goals and retreat to develop from behind the scenes.
Of course, this move had a bit of a 'burying his head in the sand' quality to it.