The markings engraved upon the souls of every Immortal Emperor's descendants were different. Those like Emperor Donghua, who attained emperorship through a Lifebound Dao Artifact, or others who attained emperorship through the hundred arts or divine abilities, would not allow such Imperial Marks to emerge among their descendants.
You could not determine in a short time what power the markings engraved upon Qian Tu's soul represented, but without a doubt, what this pattern represented indeed possessed the unique traits exclusive to an Imperial Mark—something that could neither be replicated nor imitated. This also meant that one of Qian Tu's ancestors possessed the cultivation realm of an Immortal Emperor, one whom all living beings across the All Heavens had to look up to.
As for why the other members of the Qian Clan did not possess it, there were two possibilities. The first was that the bloodline came from Qian Tu's maternal clan. The second was that this branch had grown too distant from the Immortal Emperor, so distant that its bloodline had thinned to the point where one had to return to one's ancestors to awaken as an Immortal Emperor's descendant. Both possibilities were quite likely, though you leaned more toward the latter.
After all, even if someone had truly attained emperorship through power, considering how long he had lived, his close descendants who were still alive would basically no longer exist. Thus, all his remaining descendants stood on the same starting line and could only obtain an Imperial Mark through ancestral reversion. In that case, those capable of awakening an Imperial Mark within the entire clan would be as few as the morning stars, and it would not even be unusual for there to be none at all.
Of course, according to the information recorded by the Myriad Laws