Regarding the matter spoken by the Immortal's remnant soul, Lin Jing believed it to an extent.
The tomb has a spirit!
It will treat unfamiliar grave robbers and descendants differently.
This is also an experience Lin Jing gained from a certain Immortal Palace Secret Realm, where the realm spirit acted for personal gain and benefits.
Faced with the erosion of celestial tombs during the End of Dharma Era, the tombs might prefer benefiting descendants related to its lineage rather than outsiders, offering a green light to Celestial Emperor's heirs — perhaps it was the Emperor's own consciousness all along, which is entirely possible.
This also explains why this grave robber could retreat safely from the Celestial Emperor's Tomb and survive with its blessings to this day.
