The Hammer King was famous because of the stone hammer tree, so he treated the tree as his own child. Before he died, he did not forget to arrange a retreat for his child. Although it seemed very cruel to seal the stone hammer tree here, it could ensure that the stone hammer tree would live until it met its second master.
The Hammer King's plan had succeeded. The stone hammer tree had survived, and it had even encountered the little crane grass. This was the ending that the Hammer King had hoped to see.
In the letter left behind by the Hammer King, other than these, it also mentioned another matter. That was a special technique that he had cultivated. This special technique was called the man-Plant Fusion technique, which was to fuse the man and plant as one, especially during battle.