Hmm, I noticed an interesting parallel while rereading the thread.
Nastrond: Overly militaristic, traditionally isolationist (until King Nieldun the Blood-Lusting arose).
Airgiallne: Overly militaristic, isolationist.
Now the Airgiallne King wears a mask for undisclosed reasons, what I am wondering is if he is the Shadowy counterpart to Nieldun.