I don't know what is JB idea, or what happens in his universe. But in our world, the Christian tradition says that Lucifer is not the opposite of God. God has not opposite. Literally. Lucifer and his followers fought other angels, but God is above all that.
check your mythology again, as the Adversary, before the fall, it was literally his job to oppose the status quo. Yes I know that doesn't make him opposite, though if you go back farther to the Jewish cabbala it does. God manifest is the aeon of our level of reality, literally just an Archangel,(which of course is only a piece of God, like his mouth) where as The Adversary is his dark reflection able to act in cosmic imbalance. And who takes over this Job when Lucifer falls? His wife Lilith.. Lilith as Nemesis/the Adversary is sooo thematically correct.
Eh, I'm not sure that's exactly what that means ... I think the whole "longest shadow, darkest dream" bit is more about how Mother Winter is the End Of All Things (though she may more accurately be one half of it).
'Darkness' might be ambiguous here. MW is basically entropy, I think. I'm not sure she's exactly 'evil' in the sense the Fallen are, beings that made a conscious Choice to be evil.
[And to me the way the Mothers talk about futures unfolding and Outsider victory being a final end in CD makes me think that the Mothers are limited to one universe. The destruction of any particular universe wouldn't mean "everything ends" for Uriel or Lucifer.
That may not be exactly the same thing as being of greater 'power', though. Demonreach is probably stronger than Mab on his island, but has much less ability to act. The Mothers could easily be as strong as archangels within their own universe.]
sure she is, but it's also directly correlated to size=power. Those names were not made up for no reason. Even HHWBHs boss is seeking the shadows, to corrupt or to collect. And... I tend to think that's exactly what it is, they are Archangel level power(well, when they combine anyway) holding down reality. The Creator was never bigger than the others in that way, he just has home turf advantage. Maybe I'm listening to a different conversation than you, but the way they talk implies they are NOT so limited to me. To see multiple futures unfolding all at the same time, you have to be able to exist in them simultaneously. something for instance that the gatekeeper appears unable to do in TC.
*And the hunters if shadows/shadows of the hunters bit too..
**Ooooh, and thank you for reminding me she's called darkest dream, I had forgotten.. but it fits into a theory I have that all the sleepers dream, and in dreaming create their own domain of the dream, and that would be the outer gates made manifest I think...