[The way this person talks about himself, Ithaqua feels like he's understanding less and less. Sensory input? Sensors? Not organs, nose, eyes, ears? How... odd. He doesn't know what to make of this. He has to focus but he just can't help but constantly run certain thoughts through his mind solely because of the turn this conversation has taken.]

It could have been an influence on the mind as you had mentioned earlier, or it could have been possession. With your retelling, either is possible.