Who do cultivators borrow power from?
The answer in this world is: their own descendants.
Parents have children, children have children, and generation after generation, vitality flows back along the bloodline, condensing into "heir's breath." The more descendants, disciples, and followers a person has, the more they can borrow, and the higher they can fly. So the most precious thing in this world is neither spirit stones nor cultivation techniques, but a genealogy: it bears your name, records who your descendants are, and who must send their vitality flowing back to you.
The office that controls every genealogy in the realm is the Bureau of Ancestral Lines.
For three thousand years, the Bureau has used genealogies to divide the noble from the lowly, and descendant quotas to determine life and death. Those with lengthy family trees feast on rosy clouds and drink dew, moving mountains and rivers with a thought. The childless common folk, excluded from the genealogies and valued no more than livestock, are driven to the Northern Barren Plains, where generation after generation they live as "the nameless."
What the people of the realm do not know is this: what you borrow must be repaid.
Low-ranking cultivators repay it with their lifespans, as their descendants die young. Mid-ranking cultivators repay it with their fortune, condemning their bloodlines to poverty and low status for generations. High-ranking cultivators repay it with their names, their entire bloodlines erased from the history books as if they had never been born. That is why everyone says, "Those who attain the Dao leave no descendants." It is not that they do not have children, but that they have repaid every last one of them.
And so, the higher people climb, the less human they become.
