Gu Zhen Ren
Can't FY directly use "Stealing heavenly secrets" to ask "How do I need sovereign body"? Also other than killing a venerable annexing their aperture would also require SGM.Plus they're dual cultivator. We don't know the exact mechanics but it might require double SGM in their case.
So he's confident enough in chaos tribulations and killing other venerable's now ... our mc truly has come so very far . I wonder If while not transformed into a body sovereign foetus will need similar foods too , and would refining the body back into Gu make it return to its previous self ? That's a major loss of resources for the entirety of the gu world since the rank 9 sovereign foetus only creates a rank 6 sovereign body that needs the immortal to cultivate from the beginning . Well ,these questions and the answer to them are really irrelevant though ,although I do wonder if refining the body into gu and using the gu to make another body allows it to reset its lifespan and hunger . That would be an inferior but nevertheless a form of immortality .One that severely weakens you every set year and requires immense difficulty to do though ,the only ones who can reverse refine the body into gu in this world would be Fang Yuan and Spectral Soul and them doing so will impair them , doing it repeatedly is even worse . We haven't really seen lifespan discussed in the sovereign body either .I was wondering if it doesn't have a lifespan and has the nature of gu in that it dies without food but as long as it's fed can survive without a set limit .