So the "night" of the night elves and nightborne has more to it than we thought. It was mentioned and hinted that their "shadowy" ways made the humans suspicious of these "shadowy" elves, and they stuck them with shadow meld as a racial instead of a star magic related one (which comes later in the Elune buffs of night and day).
We got some further insights in Legion, with expanded lore and more night sayings like "may the light of elune illumine you, and the night shroud you in darkness"...and we even see the wardnes use some of this magic.
Then we get the whole Night warrior arc, and we see that while Elune's light side is pure arcane energy, the dark side is pure void - this is very interesting.
Shadow may at first have been linked to death, but clearly it isn't, there is nothing about the night that is death related..but it is void related now it finally seems. And there is much more to night elves and nightborne and the night.
the shen'dralar obviously know some secrets about the void - Wrathion tries to search their libraries for more info - he obviously didn't want to ask any living one in case they might be an agent of N'zoth, anyone could be an agent of N'zoth, only the player and Magni along with M.O.T.H.E.R are aware of the full scope of what he was doing/searching for.
The nightborne are the Shal'dorei - children of the night. I wuld bet my bottom dollar they have same access to the night powers, but we just haven't seen it shown much, only the arcane half - think of the blood elves when they first came out, there was almost little to no expsorue on their light abilities or forest ranger ones, but later it shiffted tot hat. to me, Nightborne will have to be strong in three areas... arcane magic, time magic and night magic - otherwise what's the point of the name right?
so, is night basically some utilisation of the void that is inherent tot he nocturnal elven group? - is it the second of the power trinity of arcane, night and nature? It seems to fit, but obviously is not an area that is explored much.. hell the arcane part of the night elves has not been shown much in game either - only the nature part.. but a lot more is in the books.
the books do mention the Pain Mistresses of the order of Elune, but whether that is void or death magic is unknown, looking back now, it seems more likely it was void magic even though they hadn't invented void yet.