I know, I know, we finally get an expansion that gives the Legion top billing and all I want to do is talk about the Old Gods.
Still, as I mentioned in an earlier post, there are a lot of hints that while the Legion invasion is the biggest thing happening in Azeroth right now, the Legion itself might be subject to the manipulation of the Old Gods, who could be using it as a long-con to get us, the heroes of Azeroth, to unwittingly set them free.
But what freedom can these monstrosities have? What exactly is going on with them?
There have been four Old Gods on Azeroth, and while I wouldn't say Blizzard can't introduce a new one, the number seems pretty much set. We do know that there are Old Gods that have existed on other planets, and these presumably have their own qualities and identities. But on Azeroth, it appears there have only ever been four.
The first Old God to be named in-game and the first one we've been able to face, C'thun managed to corrupt members of the Anubisath and Tol'vir races (though apparently without infecting them with the Curse of Flesh) and used them along with his own Qiraji (whom he pretty much created whole cloth, I think, or at least their Aqir ancestors) to transform Ahn'Qiraj, originally a Titan installation meant to serve as his prison, into the capital of his own evil empire. Ahn'Qiraj was sealed away by the Bronze Dragonflight after the War of the Shifting Sands a thousand years ago (yes, there are things that happened between the War of the Ancients and the oddly-titled First War!)
When the Qiraji tried to launch another war (somehow breaking through the seal... but then we had to open the seal... look, I wasn't playing yet at that point) the heroes of Azeroth banded together to war against the Qiraji and took the fight into Ahn'Qiraj, ultimately slaying C'thun.
But Old Gods are enormous, and the thing that we fought may have been an important part of the creature, it seems highly unlikely that C'thun was truly killed.
In fact, we know that something of C'thun remained, because later, Cho'gall would travel to Ahn'Qiraj and be "blessed" by C'thun, growing eyes all over his body and a cephalopod-like beak on one of his heads. Some would even begin to call him "Cho'thun." We would then slay Cho'gall in the Bastion of Twilight.
Here's the question: was this simply a blessing from the Old God, or did Cho'gall actually take on the essence of C'thun? By killing Cho'gall, did we also permanently kill C'thun? Or does C'thun remain beneath southern Kalimdor, perhaps having lost (maybe temporarily) the ability to commune with his Qiraji subjects within the Temple, but still very much alive and a threat?
Yogg-Saron's prison also happened to be the main headquarters of the Keepers on Azeroth, which maybe was not a great plan, actually. After Odyn left in a huff because the Keepers wanted to empower dragons (evolved from organic life that itself evolved from native elementals) rather than a Titanforged race like the Vrykul to serve as Azeroth's greatest protectors, Loken was left in charge of Ulduar. And after he had an affair with Thorim's wife Sif and then accidentally (maybe accidentally) killed her when she wanted to break the affair off, his paranoia in covering up the murder made it easy for Yogg-Saron to get into his head and make him do a bunch of awful things, including programing the Curse of Flesh into the Forge of Wills.
Indeed, Yogg-Saron's machinations on Azeroth might be the most impactful of all the Old Gods. Not only did he effectively create the Curse of Flesh, but he also created the Emerald Nightmare after well-intentioned Druids planted Vordrassil in Grizzly Hills unaware that its roots would connect with the Old God's own tendrils.
After taking over Loken's mind, Yogg-Saron pretty much manipulated him into giving him control of Ulduar for countless years.
So what about now?
Well, we of course went into Ulduar and fought him. And in theory, we killed him.
Here's why I'm more convinced that Yogg-Saron is dead-dead than C'thun. When fighting C'thun, you kill him by entering what appears to be his stomach (probably one of many) and disabling his damage immunities from the inside. A stomach is certainly important, but it's something that you could theoretically live without, especially if you're an incredibly-hard-to-kill Lovecraftian monstrosity.
When we fight Yogg-Saron, we enter his brain. It is by attacking his brain that we are able to finally slay him, and that suggest to me that if Yogg-Saron is still alive in any way, he could very well be brain-dead - essentially just a mass of flesh that yes, probably radiates dangerous void magic, but is incapable of true intentional menace.
On the other hand, that may have been one nerve cluster among many. Still, I'm guessing that Yogg-Saron is far less likely to recover from our fight with him than C'thun is.
Y'Shaarj was apparently the most powerful of the Old Gods during the days of the Black Empire, but he's also the one that is absolutely explicitly dead. Aman'thul didn't pluck something the size of the things we fought in AQ40 and Ulduar out of the crust of Azeroth. It's implied he really grabbed the whole body, even the tendrils digging down toward the World-Soul, and pulled him out, root and stem.
So Y'Shaarj (it bugs me a little that it's pronounced "Yah-sha-raj" but oh well) is dead as dead can be. During Mists of Pandaria, the implication seemed to be that the reason the Titans then decided this had been a bad idea was that Y'Shaarj created the Sha with his dying breath, and that perhaps killing an Old God would result in such a curse.
Later, in Chronicle, we found out that while this was certainly a bad thing, the biggest problem was that pulling Y'Shaarj out created a gaping wound in the planet (the Well of Eternity) that threatened the life of the World Soul.
As far as we know, there were only really two remnants of Y'Shaarj. The Sha were, in a sense, more like a permanent spell effect of his - they were separate enough from the Old God himself that the Klaaxi - who still absolutely worshipped the Old Gods - still found their effect on the Empress to be anathema.
The other remnant was the Heart of Y'Shaarj - literally the monstrosity's heart, which was sealed away by the Titanforged for safe keeping, and was used by Garrosh Hellscream as a weapon against his foes.
I believe that the official story is that when Garrosh bled the remaining power out of the Heart, and we defeated him nonetheless, the very last of Y'Shaarj's essence was purged. In fact, lorewise, the Sha might not even exist anymore. Even if they still do, the Heart and the corruption it inflicted on the Vale of Eternal Blossoms are both definitely on their way out.
Returning to C'thun, the reason I speculated that killing Cho'gall while he was carrying the essence of C'thun might mean the permanent end of C'thun is that we basically did that with Garrosh. Garrosh of course took the power of the Heart by force, and it didn't seem to have a real influence on him (he was pretty evil, but I think that's just because he was a fascist asshole, not any supernatural corruption,) while Cho'gall was utterly devoted to the Old Gods. Still, if the mechanics were basically the same, C'thun might be gone gone.
So now we come to N'Zoth. Interestingly, three expansions in a row we got a new Old God named for us. But while we fought Yogg-Saron and Y'Shaarj's influence was felt throughout Mists of Pandaria, N'Zoth was never more than a background influence.
N'Zoth was first talked about I believe in the Dragon Soul raid (I could be wrong about that, but it was definitely in Catalcysm.) N'Zoth seemed personally invested in Deathwing's plan for destruction. The second and third bosses of Dragon Soul were some of N'Zoth's top minions.
While there was some implication that Yogg-Saron had been the one to corrupt Deathwing, N'Zoth may have been the primary force driving him instead.
N'Zoth also seems to have a strong tie to the Emerald Nightmare. While we know that Yogg-Saron is the one who created it, N'Zoth clearly has a great presence within it. When defeating Il'gynoth, which appears to be the purest manifestation of the Nightmare's corruption, he/it/whatever says "N'Zoth, I go to Ny'alotha."
Ny'alotha has been mentioned before by the Puzzle Box of Yogg-Saron - a toy gained through archaeology that is basically a lore-speculation-fodder-generator.
The Puzzle Box implies that Ny'alotha is probably under the ocean, and is most likely where N'Zoth is imprisoned.
When Whispers of the Old Gods was released for Hearthtstone, we actually got our first look at both N'Zoth and Y'Shaarj. The latter looked fairly similar to the Sha he spawned. N'Zoth looks a lot like a giant kraken - meaning that beings like Ozumat and all those other evil cephalopods you find in Vashjir are probably his creation.
In fact, toward the end of the Vashj'ir quests, you find that the massive L'ghorek is being corrupted by these massive tentacles reaching up into its shell. These things are so huge that kind of can't imagine they're anyone's but N'Zoth's.
Clearly we haven't interacted directly with N'Zoth, so it's most likely that he's still around. In fact, in a way, N'Zoth might be the last Old God standing, which could potentially give him a lot of power (by the way, I'm saying "him" but I should really be saying "it.")
Ny'alotha could be a titan facility meant to keep him trapped, though I'd guess that, much like Ahn'Qiraj and Ulduar, he's probably running the show there by this point.
If the tentacles attempting to corrupt L'ghorek are actually his, then that would place N'Zoth and by association Ny'alotha somewhere in the Great Sea, probably to the east.
Unfortunately I lent my copy of Chronicle to a friend, so I can't check where exactly his territory was during the Black Empire, but I'm pretty sure that it includes, well, the area that we now call the Broken Isles.
I feel pretty confident that between the Nightmare, the presence of Neltharion's Lair (which is probably where he started to get corrupted into Deathwing,) and the evidence that the Legion's invasion might be part of an Old God plot, N'Zoth is doing some serious behind-the-scenes shenanigans.