They've been teasing the Death > Void for a long time.
Denathrius/Malganis will kill Xalatath at the end of March on Queldanas and take over the Sunwell
12.1/2 will bring in the Venthyr and specifically Kaelthas.

>>713449332
>Xalatath and a bunch of cultists are doing Void shit to the Sunwell
>she's all confident and shit. Giving villain speech
>suddenly the Sunwell turns red
>Xalatath gets confused
>all the cultists turn back into Nathrezim
>Mal'ganis stabs Xalatath with Remornia
>"Thank you, Harbinger. Without you, it would've taken significantly more effort to restore the Master."
>he throws Remornia into the Sunwell
>Denathrius climbs out