I have some concerns that solar brilliance would be abusable. A strong astral nation could have one mage cast solar brilliance, another antimagic, give them some bodyguards, and blind a good percentage of an opponent's army. You may well sacrifice the mages/bodyguards - but it would be worth it.
Sure, you can do this in a normal game but there your opponent might have recourse to GoH, Chalice, even faery queens or a mage swap with a nation that has healers. Also, a normal game transitions to SCs, who aren't threatened by solar brilliance, whereas this game won't (though it's possible thugs will end up dominating the field of battle).
With the current nation lineup it's mainly Agartha that will really be able to take advantage of darkness. I'm more inclined to give them a chance to shine than to help out astral nations.
