I can see how Nox Noctis would be an excellent defence against conventional Stacks of Doom, but it is not a game breaking feature. If you simply must launch an invasion into NN territory, just follow one of the following tactics:
1) Rush Warhorses and build Ride of the Nine Kings, build a city cracking force of Knights and Chariots. Use Hawks to seek weak frontiers and raze. Bonus: you'll have a strong and mobile counter-attack force for defence.
2) Sorcery, Fireballs, and the Tower of Elements. With Spell Extension I and II your mages never need leave the safety of your borders: with Haste and Mobility I you can bring your mages to your border, summon your fireballs, and flee back to your secure interior. Spam Tigers or Skeletons, or build a few Mobility II horsemen to take and raze the city.
I could probably think of more, but am pressed for time.
1. hahahahahahahaha you gotta be kidding me! Rush Warhorses? that's your strategy? why not rush mitheral weapons? or future tech 4? the mere fact that you have to "Rush" a late game tech shows how overpowered ONE building is.
2. fireballs and tigers eh? I'm sure all those longbows and champions stationed in the city are shaking in their boots. it's not like they could...oh i don't know, FIREBALL YOU BACK!
Definition of Overpowered
countering:
archer spam: build catapults.
magic stacks: assassins.
warrior spam: shock upgrades.
Turtleing civ: pillage improvements.
assassins: assassins&guardsmen
tough stacks: heavy magic and assassins
NOX NOCTIS: ALL OF THE ABOVE, only double the forces you bring and prepare to have most of your forces dwindle the longer you stay in the territory.
-and it only cost him a great prophet.