I've frequently wondered how exactly the Emerald Nightmare fits in with the Burning Legion's invasion. Xavius is a demon, technically (much as the Man'ari is the form Eredar - who presumably would otherwise be just like the Draenei - take upon becoming demons, it seems that Night Elves who undergo this transformation become Satyrs,) and given that there's a massive doomguard assaulting the Temple of Elune in Val'sharah along with the forces of the Nightmare, it would seem that the Nightmare is part of the Legion's general invasion force.
First off, the Legion very clearly leaves the worlds they touch looking the same - the earth charred black, flowing with Fel-green lava and generally broken and adrift in space or the Twisting Nether.
The Nightmare looks very different than that. And the Nightmare is not a creation of the Burning Legion. It is a creation of the Old Gods, whom the Burning Legion was technically created to oppose (along with any bleeding-heart Titans who weren't getting on board the "destroy the universe to save it from the Void" train.)
Xavius may indeed have his loyalties with the Legion, but while he has dominion over the Nightmare, he is not the Nightmare itself.
I have not run Emerald Nightmare yet - I'm likely going to do the first wing of LFR next week and write all about it here - but I have followed some forum posts (such as this one on the WoW forums) about the whispers that Il'gynoth speaks during the fight against him.
In case you haven't been looking into the raid, Il'gynoth is the most Lovecraftian boss creature in the raid, an amorphous blob with lots of eyes and tentacles, and is referred to as a pure manifestation of the Nightmare.
As we often get in Old God-related stuff, Il'gynoth whispers to you, and thanks to DK Cirno on the forum, we have a few of its quotes. I don't know if this is all of them or just some, but damn are they food for thought:
(EDIT: Of course there's the big caveat that an Old God-affiliated monstrosity might be trying to lure us into false conclusions. But for the purpose of this post, let's assume that Il'gynoth is at best manipulating us with truths, rather than lies.)
"To find him, drown yourself in a circle of stars."
So of course we have no idea who "he" is. This could be N'zoth, the last Old God whom we have been unable to locate. As to a circle of stars? That's a good question.
One thing I've been wondering about, lorewise, is what the hell the Nightwell is. The Well of Eternity was the blood of the Titan Azeroth (we get this from a presumably omniscient source in Chronicle,) and the Sunwell and the quasi-Well that feeds Nordrassil on Mount Hyjal were both created using vials of water from the original Well.
So what is the Nightwell? It had to exist before the War of the Ancients, as Suramar City was totally cut off from the rest of the world after that point. It is a font of Arcane energy, which sure sounds like it could be tapping into the lifeblood of Azeroth. Perhaps some very ancient Night Elves figured out what the Well was and decided to make another incision?
It's tenuous, certainly, but what if the circle of stars is Suramar City? What if the Nightwell is tapping into something else entirely? Could the Nightwell be feeding on N'zoth?
Or more likely, we don't yet know what this Circle of Stars refers to.
"The boy-king serves at the master's table. Three lies he will offer you."
The most obvious boy-king would be Anduin Wrynn, who is king (again, but for real this time) with Varian's death. And being thrust into this position while Azeroth is in her greatest crisis certainly sounds like he's being put at the big-boys' table. But what about these lies? What would Anduin lie to us about?
Or is it Anduin?
It could also apply to Wrathion, who is now "king" of the Black Dragonflight. Granted, there's only one other black dragon on Azeroth than him and the two are probably not aware of one another (and also probably not aware that the other is uncorrupted.) But Wrathion sure doesn't hesitate to lie to us.
"Her heart is a crater, and we have filled it."
Ok, here's something worrying. We don't know who this refers to, but I can think of two possibilities.
One: Jaina. The city she poured her heart and soul into was reduced to a crater in the middle of the war between the Alliance and Horde. Ever since Theramore's destruction, things have been pretty terrible for Jaina Proudmoore. But we've also watched as someone who used to strongly advocate for peace with the Horde has become one of if not the strongest advocates of destroying it.
Now, there's plenty here that I think could be explained in mundane terms. The very fact that she was such a proponent of peace could be why she has turned so much against it - if even as this advocate of cooperation, she could still be attacked and have her city - a city whose gates she opened to the Horde at the cost of her own father in order to further the cause of peace - destroyed, then surely there was no more reason to ever trust the Horde again.
But if this quote refers to her, then we've got a bigger problem - Jaina's hatred of the Horde may not be simply a result of trauma and frustration. It may be the result of the meddling of the Old Gods.
But the far worse possibility is Azeroth.
When Y'shaarj was torn out of the crust of the planet, it left a gaping wound, bleeding profusely. This was the Well of Eternity. Given how much this worried the other Titans - that they chose to leave the other Old Gods alive rather than extract them as well - it could be that the Titan Azeroth's heart was where this crater was made.
And the Old Gods' purpose in being is to corrupt the Titan Azeroth, meaning that if this is true, and referring to her, then we're in serious trouble. Hell, the Legion might actually be justified in this invasion (though it's unlikely they know her status any better than we do.)
"The Lord of Ravens will turn the key."
Ok, lord of ravens? Well, there's Ravencrest, of course, but he's dead (though he's a ghost and has interacted with us, even aiding us once we demonstrate that he's been tricked by demons.) The other possibility is Medivh, of course, who is kind of associated with Ravens as well.
In fact, we know that there will be a boss in Karazhan called Shade of Medivh - is that his future role?
And of course there's Odyn as well, the Titan Keeper who has a pair of immortal ravens as his companions (like his Norse-mythology antecedent.)
(EDIT: There is, of course, also Khadgar, who has taken Atiesh as his own staff and even comments on how he likes using the staff's Raven form to travel around. Given that he's more or less coordinating the expedition to the Broken Isles and is also kind of known for his ability to close portals - see Warcraft II - he might be involved in this key-turning situation.)
But also, what key? We'll come back to this.
"The King of Diamonds has been made a pawn."
Ok, first off, that's mixing card and chess metaphors... but oh crap. The King of Diamonds is almost certainly Magni - he's a king, and he's now made of diamonds.
But being made a pawn means he is being manipulated. Magni has become the speaker for the Titan Azeroth. But historically, people getting telepathic communications from voices deep within the earth have not always turned out well.
What if Magni's mistaken? What if it's not Azeroth, but the Old Gods who have been speaking to him? Or, if the "heart is a crater" quote is referring to Azeroth, perhaps he is, indeed, hearing from Azeroth, but Azeroth no longer has our best interests at heart.
(EDIT: Of course, given Il'gynoth's presumed antipathy toward Titans, there could be a more innocent reading of this - that Magni, once king of his people, is now in the role of a servant to a greater power, namely Azeroth.)
"Five keys to open our way. Five torches to light our path."
Right, so here's something worrying. There are five pillars of creation that we're collecting on the Broken Isles. I imagine most people who have hit 110 have four of the five - the fifth being in Suramar and probably requiring you to finish all the major quests there (I need about 3000 reputation to get the next quests.)
We've been told that these five pillars of creation are the key to closing the portal at the Tomb of Sargeras.
And they might do that. But what exactly were they used for in the first place?
What if these were the artifacts used to imprison the Old Gods? And what if by using them to defeat the Legion, we wind up releasing the Old Gods?
"Flesh is his gift. He is your true creator."
Well, the Curse of Flesh is kind of an odd thing - on one hand, it was created by Yogg-Saron (implemented by Loken once Yogg-Saron had him under his control) in order to corrupt and ruin the Titans' creations. But it also allowed the races of Azeroth to have free will and evolve in directions the Titans had not anticipated.
Honestly, this one is less worrying than simply a kind of propagandistic opinion. The mortal races of Azeroth are, in a sense, an unwitting collaboration between the Titans and the Old Gods.
To put this all together:
My guess is that this is referring to events that will occur toward the end of Legion - we will be victorious in some way (after all, the game has got to survive) but much as we freed Gul'dan at the beginning of Warlords and are now paying the price for that, I imagine that our plan with the Pillars of Creation is going to have some serious negative repercussions.
I don't know if Blizzard would want to follow up Legion with a full-on Old God expansion out of fear of burning out all the biggest threats in the Warcraft cosmos, but I do think that somewhere down the road, our use of the Pillars of Creation may indeed see us unleashing the Old Gods.
So I'm making this prediction here: I'm not saying it'll be the next expansion or even that the name will be right, but I'm predicting that some day, we'll get World of Warcraft: Rise of the Black Empire.
Check again in a year or more to see if I'm right (but not necessarily wrong!)