WARNING: MAJOR Midnight Spoilers in this post!
The Story of Voidspire
Before this cinematic occurs, we first fight our way through the Voidspire raid. While battling domanaar, void creatures, and even the return of Nexus-King Salhadaar, our allies in the Vanguard of the Light become increasingly paranoid and distrustful of the void elf allies they fight alongside. That paranoia ultimately culminates in the Vanguard's leaders being overtaken by 'Lightblindness', who we are forced to kill.
Along the way, Xal'atath taunts Alleria throughout the raid, goading her into violence with reminders of Turalyon's similar actions towards their son Arator in Eversong. Enraged, Alleria pursues Xal'atath to the Crown of the Cosmos atop the Voidspire, where she is overloaded with Void energy and forced to fight us at full strength. Upon subduing Alleria at 1% health, the cinematic plays.
Xal'atath yells: Oh, Alleria. If I had known you would all simply kill each other, I wouldn't have gone through all this effort.
Xal'atath yells: But perhaps I shouldn't be surprised. Not after Turalyon cut open your own son.
Alleria Windrunner yells: Enough! I'll rip out your tongue, Xal'atath!
Arator yells: Mother, wait!
High Exarch Turalyon yells: We can't let her face Xal'atath alone! Umbric, bring everyone up there!
Magister Umbric says: This may feel a little uncomfortable.
Magister Umbric says: We must make haste. Xal'atath is using Alleria's rage and pain to erode her mastery over the Void.
Magister Umbric says: After what happened with Turalyon and Arator... I can see how Alleria would struggle to maintain control. I doubt I'd be able to, if it were me.
Arator yells: Mother!
High Exarch Turalyon yells: Alleria!
Xal'atath yells: How touching. Your family has come to say goodbye.
Xal'atath yells: Ah, and my favorite champions as well! I was afraid you might miss this.
Arator yells: What are you doing to her?!
Xal'atath yells: Keeping my promise, of course. Taking everything she loves. Leaving her with nothing but the Void.
The Dark Naaru L'ura
The biggest reveal in this cinematic is that Xal'atath was never actually trying to corrupt Alleria: she was trying to access the dark naaru L'ura inside of her the entire time. This reframes quite a lot of Xal'atath's actions over the last few expansions. Her constantly goading of Alleria, her allegiance with us to defeat Dimensius, even her very reason for creating the Voidspire, it was all in pursuit of L'ura... or something like her, at least.
L'ura is but one of multiple dark naaru we have seen throughout Warcraft's history. A number of them have appeared on Outland where were either destroyed or purified, and the Sunwell itself was re-ignited by the purified heart of a dark naaru. Most recently however, we saw a dark naaru named T'era present during our leveling campaign in Voidstorm, only just transformed by the Shadowguard ethereals.
While T'era's purpose during leveling was never addressed, this cinematic makes the purpose of Xal'atath's machinations much clearer. Throughout Voidstorm, we meet many domanaar who make a habit of kidnapping mortals from various worlds across the Great Dark Beyond, and with the power at her disposal thanks to our defeat of Dimensius, Xal'atath was able to force those domanaar into her servitude and point them towards Azeroth.
Utilizing those domanaar, Xal'atath also kidnapped T'era from the draenei world of Nashabor, likely with the intent of utiliizing it to corrupt the Sunwell. Thanks to Alleria's intervention, T'era was killed before it was able to put to use, but now her own dark naaru L'ura is being used in its place.
Corruption of the Sunwell
The reason why Xal'atath needs a dark naaru likely lies in the Sunwell itself. During The Burning Crusade, Lady Liadrin and Magister Astalor Bloodsworn drained the Light from a captured naaru named M'uru to fuel the powers of the Blood Knights. In the process, M'uru was turned into a dark naaru, who we defeated during our original assault on the Sunwell Plateau. In the aftermath, the Prophet Velen purified M'uru's heart and placed it into the Sunwell, re-igniting it into the holy fount of power we know today.
Utilizing the now-freed L'ura, the Sunwell has been transformed by Xal'atath into the Darkwell, with a beam of darkness now piercing into the Isle of Quel'Danas. The surrounding Sunwell Plateau has been overtaken by forces of the Void and the Twilight's Blade, marking a sound defeat for us.
Xal'atath's exact reason for doing this has yet to be revealed, but the answer may lie in the Sunwell's other innate properties. While it is known mostly as a holy well today, its original creation by the high elves was as a new source of arcane magic for their people. They chose its location on the Isle of Quel'Danas due to its massive connection of ley lines, veins of arcane energy that course throughout Azeroth's surface.
Utilizing a place of such power, Xal'atath would likely have a much easier time of achieving her stated goal of claiming Azeroth's Worldsoul, but we will have to wait for the finale of March on Quel'Danas to see just how successful her attempt via the Sunwell ends up being.
The Fate of Alleria and Turalyon
Along with the removal of the dark naaru inside of her, Xal'atath also leaves Alleria with one final twist of the knife -- literally. Using the vessel that once held her, Xal'atath wounds Alleria quite severely, possibly even killing her.
Some signs may point to Alleria not being entirely dead, however. Alleria's body is quite limp after Xal'atath discards her, but when the platform is later destroyed and the Windrunner family are sent falling, her eyes are open. This could be simply the sign of a corpse unable to control itself in freefall, but it seems unlikely for Alleria to go out in such a fashion after so many years of focus.
Turalyon and Arator are also present with her when the Darkwell swallows them up, but while Arator is teleported to safety (thanks to the foresight of Umbric and the arcane tether he created prior to our entry into Voidstorm), Turalyon is sent spiraling down into darkness alongside Alleria.
In addition to the star-crossed couple, the quests following the raid also reveal that the Vanguard of the Light has also been defeated, with its surviving members either vanishing entirely or being left indisposed surrounding the Sunwell Plateau. While this adds stakes to our next steps of cleansing the Sunwell in the March on Quel'Danas raid, it also begs the question: where did Alleria and Turalyon go?
This is a question the WoW community is far from foreign to, having asked it for over a decade prior to their return in Legion, and it rears its head yet again. It's possible that once we cleanse the Sunwell, the two of them will reappear, but if we tie back to the previous speculation of Xal'atath's purpose for corrupting the Sunwell, it is possible that they may not be seen again until much later in Midnight when Xal'atath's full plan with the Darkwell is revealed.
Bonus: The Blade of the Black Empire
Alongside the more major, plot relevant reveals, Xal'atath also sneaks in an extra surprise: she is in possession of the Blade of the Black Empire.
The last time we saw the dagger, it was used as a vital asset in the defeat of N'zoth, but mysteriously vanished just before the Old God's death. There have been many hints over the past few expansions that N'zoth may not have been as soundly defeated as we thought, but Xal'atath having possession of the dagger certainly throws a wrench in those theories.
...Or does it?
WARNING: Patch 12.0.5 Datamining Spoilers!
In patch 12.0.5, we will seemingly witness the return of N'zoth. In the game's files, there is a new version of N'zoth's model that Wowhead has datamined, looking much worse for wear and a bit less mighty than last time we saw him.
Alongside this, we also see the resurgence of the naga in the upcoming Void Assaults, last seen in significant numbers under the command of N'zoth. If N'zoth did escape through the dagger, it is possible that his bargain with Xal'atath culminated in his freedom in exchange for the dagger's further use at her hands. This model may indicate that he is out and about once more, albeit in a weakened form similar to Xal'atath herself before we aided her during Battle for Azeroth.
Regardless of the answer to the mystery of how Xal'atath obtained her former vessel, she has used it to great effect in this one cinematic to defeat Alleria, claim her dark naaru, and transform the Sunwell into a vessel of dark power for her plans. We won't have to wait long to see how these plans further unfold, with the March on Quel'Danas raid releasing on March 31st along with more cinematics!
