Not necessarily a mistake, but I wonder about Kellhus' statement to Proyas along the lines of "It would frighten you learn how little of our foe I truly know."
On the one hand, I feel like Kellhus must have figured out a ridiculous amount by the time of the Great Ordeal. On the other hand, the Consult is still remote and mysterious as far as we can tell, and Kellhus seemed to have been giving Proyas some truth about Akka, so could this be reliable?