Sword Master: Why Can't This Sword Cut Through the Other Side?

Gu Changming has practiced swordsmanship for three thousand years, and after sitting on the Taoist throne, he has no rival in the world. But it took him three hundred years, but he still couldn't open the door to the other side. Since the door can't be opened, let's cut the lock first. The current sword master put away his sword and went down the mountain, deciding to ask someone.