Inb4 after all this speculation there's some loop-closing switcheroo, like Eighth Umbral G'raha using his blood (confirmed to be the catalyst between the spiritual aether - soul, mind, and memory - and corporeal aether - the body) to transfer his memories to Source G'raha, who wakes up one day, goes back in time trusting his visions and having faith in the narrative that this is how it has to be, and now that loop is "the way it always was" (from the illusory 3D perspective where time isn't all happening at once). The Eighth Umbral Era, an "illusion" that "never happened".
But then how did all that Ironworks stuff get into the basement. Bah.