I bet it's been brought up, but it makes a lot of sense that the Heart is Nau-Cayuti's. It would be difficult, I guess, for Ses to make a sorcerous artifact out of his own heart. Perhaps it wouldn't be so hard to copy/paste into another heart. The legend holds that the Consult collected NG's remains, but maybe Ses did and intended to set one piece of it beyond their reach (Atyersus). Ses could load his memories into NC's heart and it would be "Seswatha's Heart" in the same sense that the meat that Kellhus pulled out of his chest was "Serwe's Heart." The heart that possesses. For Bakker's purposes, it would mean that Akka might glean some insight into the NG's state and how to fight it. The Consult will think of everything, but they might not suspect this.