All from Wowhead – some great reading –
In the Crucible of Storms update, the Old Gods take a central role in the new quests and raid.
N’Zoth – God of the Deep
N’Zoth is one of the four Old Gods of Azeroth, long considered to be the weakest of the Old Gods but the only surviving Old God in Battle for Azeroth. During the introduction questline to the Crucible of Storms raid, it is discovered that part of N’Zoth is actually inside the raid. Players unwittingly help N’Zoth by bringing three relics of power for him, as well as freeing Xal’atath from her dagger.
https://www.wowhead.com/guides/lore-of-old-god-nzoth
Xal’atath
Xal’atath is an ancient being, dating from back when the Black Empire ruled Azeroth. It is not known how Xal’atath and the dagger became one being. Some rumors say that the being in the dagger is all the remains of a forgotten Old God, consumed by its kin at the early ages of the Black Empire. Others say that the dagger is one of the many claws of Yogg-Saron, ripped from the monstrous Old God and used by their servants in ritualistic sacrifices.
In Patch 8.1.5, Xal’atath, with the help of the player, separates from the Blade of the Black Empire and leads us into the Crucible of Storms to receive the Gift of N’Zoth.
https://www.wowhead.com/…/lore-of-xalatath-and-the-blade-of…
Sylvanas Windrunner
Sylvanas is one of the most tragic and controversial figures in Warcraft. Following Dazar’alor, she revived Derek Proudmoore, knew Baine reunited Derek with Jaina, and then publicly arrested him. While her endgame remains unclear in 8.2 datamining, the Horde player willingly gives her the Blade of the Black Empire, upon clearing Crucible of Storms.
https://www.wowhead.com/guides/lore-of-sylvanas-windrunner
Queen Azshara
Queen Azshara is the ruler of the naga, overseeing their activities from the sunken city of Najzatar. She was once the ruler of the night elves, being beloved by both Kaldorei and Highborne alike. Being one of the most beautiful and powerful beings to ever exist in Azeroth, her Alliance with Sargeras and the Burning Legion led to her downfall, destroying both the Kaldorei empire and sundering Azeroth itself during the War of the Ancients.
However, she was not completely defeated after the Sundering, striking a pact with the Old God N’Zoth and saving the Highborne by transforming them and creating the naga race. Now acting as one of the rulers of the oceans, Azshara continues plotting to rid the world of what she perceives as inferior races. We do not face her in 8.1.5, but we battle one of her most-trusted lieutenants, Uu’nat, in the Crucible of Storms raid.
https://www.wowhead.com/guides/lore-of-queen-azshara
History of N’Zoth and the story of the Crucible of Storms raid
https://www.wowhead.com/…/story-of-crucible-of-storms-and-n…
None the Wiser Guild 