As I am a Nighbtborne/Highborne geek, I will write down about the Nightborne.
The Nightborne are the imagine of the Highborne elves of the Kaldorei Empire, if the Highborne of the Kaldorei Empire, would prosper the same way they did before the world sundering, the would be very similar if not exactly like the Nightborne.
A snobby, noble, and xenophobic aristocratic nobles this is a Nightborne.
Fun fact, many of the Nightborne still consider themselves the Highborne, and they think they are the true owners as well as the true protectors of the Quel’dorei culture of the Kal’dorei Empire.
The Nightborne unlike their other cousins, have saved traditions of the Highborne society, meaning the Nightborne still do have Noble houses, the ranks between the society, the Highborne and the Commoners, a socials ranks which were banished from the Kal’dorei, Sin’dorei, Quel’dorei and the Ren’dorei.
Another main tradition they have saved is Tal’ashar, a honor duel, whereby someone may challenge another person to individual combat, it is same as the Mak’gora of the Orcs.
Many of the priestesses of Elune has most likely turned into astromancers after the closing the of the Suramar. The highborne of Suramar were studying the stars as early as twelve thousand years ago, The nightborne kept on with their studies, and inside the Nighthold is an area called the Astromancer’s Rise.
Star Augur Etraeus seen using void priest spell during the encounter as well.
However, in Suramar, you may see some Nightborne kneeling in-front a statue with a half moon scythe on her hands.
Could it the image of Elune for the Nightbonre?
We yet to find.