Darkwhisper

The Darkwhisper were a sect of cultists loyal to N'Zoth, led by Dark Inquisitor Xanesh and commanded by Vexiona. They infiltrated Blackwing Descent and repurposed its laboratories to conduct experiments on twilight dragons, feeding the failures to a spawn of Shad'har the Insatiable. Vexiona revealed their assault as a ruse to capture Wrathion and use his essence to raise his siblings Onyxia and Nefarian as servants of N'Zoth, though their plot was ultimately foiled by Wrathion and his companions.

It is unknown what happens or remains of the cult after the death of their leader, however, it is most probably that the cult is no more after the destruction of the Black Empire and N'Zoth at the hands of Azeroth's champions.