But pure aether is still aether right? While he stated that there is no trace of aether left. We also learned that time works different in the void. So maybe for them the flood has not happened that long ago. We do also know that there is a hierarchy and that these void sents come to other worlds to eat the aether and that also fight among themselves to get the aether of each other.

So taking his words into account and that we learned that time runs different between shards and especially in the void, I would assume that its true that there is no aether left thus I just see no way right now to save that shard. Because if all that is needed is a darkness aspected Eden then why did the Ascians never use that? These beings that lived for thousands of years and have three originals among them? Seeing how they saw it as a mistake and maybe even a limitation on Zodiark, I would say that they have already tried everything they could do change that.