I have a question... What exactly did the myth's say that the Goddess Nyx's powers were? Besides the Night?
I have not found anything specific about her powers. She was one of the primeval gods, born from the initial Chaos. Both gods and men feared her. Zeus himself was afraid of her, so she must have been very powerful. My personal interpretation is that maybe everyone is afraid of her because man has always feared darkness and the dangers that it brings.
In the later writers of the antiquity, she becomes more and more just a personification of the night.
I have read that she lived in a cave where she gave oracles, so probably she had the power of prophesizing. Sometimes the sorceresses (such as Circe and Medea) invoked her, even if she is not a goddess of witchcraft.
I have also read that, in the Orphic poetry, she chants inside the cave, while Adrastea, who is outside, clashes cymbals, so that the whole universe moves to the rhythm of Nyx's chanting - from this, it seems that Nyx is the one who keeps the universe moving (but I have not found - yet - the respective text in the different Orphic hymns, I'm still looking).
Hope that helps... at least a little!