ARandomMob
You know what, Imma just call it. The curruption the Shogun was trying avoid, maybe all those years of " Eternity" is what really currupted her. And since she's alone, no one could tell her otherwise. After all, who would dare tell the God of their land that they began to stray. Like an episode of madness. Who knows, maybe the fight with travelor purified her. Its easy to fool yourself into thinking you're fine, especially someone as thick headed as Ei.
By the way, since you want to do a crossover with XCP, why not show that the Thing is just another Aeon? Only the one that is stupidly hidden and dominates the path of the Afterlife or the Soul? That is, literally the first Aeon that appeared? Well, or itâs trivial to mention that this is probably the Eon of Nothingness, according to the description they are quite similar, and the scene with Acheron and Aventurine in Penaconia will suit your idea even more. But it's true, it just came to mind in the morning