After you kill Xavius, he turns back into a Night Elf & the whole raid of the Emerald Nightmare turns back to the Emerald Dream but what caught my interest was when I went into the tree-cave [represents a purified il'gnyoth] you can see Ysera's spirit walking in and out of it constantly fading visible and invisible but whats most creepy is that theres this tall flower with void energy swarming around it called "Remnant of the Void". If you're a shadow priest the daggers tells you that something that is bound is having its bindings get weaker and that we must prepare to defeat it. Perhaps N'zoth
This is what the dagger says:
"Almost completely gone, as if it never existed. But the Rift is deep and vast, and somewhere down there it stirs. Something has changed, the last prison weakens. We must prepare."