Han Shang spoke in a calm, emotionless tone: "The old boss once said that the old gentleman is a meticulous person; everything he does has a logic behind it. Clearly, this matter is no exception."
Han Shang's implication was clear: a person like the old gentleman would never do something futile.
Everything he does must have a purpose. By this logic, the deed is indeed a useful thing.
On careful thought, it's exactly that. Yanggou Village is heavily guarded, serving as the first line of defense; the eight tombstones, filled with mysteries, count as the second line of defense; plus, the various traps within the Ancient Tomb constitute the third line of defense.
The old man's design of the defense lines was already challenging enough. Without a map, it would be nearly impossible to crack the code. So, when the original rules were set, the old man added a note: having the deed is equivalent to having the map, explicitly telling you the solution.
