So skirk said that the gnosis is made by the third descenders remains right? (But we also know that the sovereign's power (dominion over the element) can be returned via destroying the archon seat? Or maybe even by passing it on (this is just a theory))
There's a big chance the Tsaritsa is not collecting the gnosis for its power but for the remains, that by collecting all of it they can resurrect the third descendant.
I have a feeling its the abyss twin's or what is left of them. There must be reason why they are counted as someone from Teyvat. Either it's because they manipulated the leylines or because they were resurrectted already, but a botched resurrection via Natlan.
That by resurrecting the abyss twin from their original body, they'll get their full powers back and even durability, so the war against fate and Celestia might have more promising end.
This is just a theory tho.