The Dao. What was Dao?
Wang Lin's life and death cycle, karma cycle, and the change of true and false were all Dao that he had comprehended by himself, or perhaps it was a change in his thoughts. He had gone from an unknown cultivator to where he was now, able to stand among the strongest. This change was also Wang Lin's growth.
From the cycle of life and death, he could see through life and death. That was why he could struggle in the face of danger and find life in the face of death. In the end, it made him want to defy the heavens and become an Inverse Cultivator.
The path of inverse cultivation was to see through life and death without fear! All of this was the obsession and thoughts that the life and death domain gave Wang Lin.