So the other day I officially predicted that the next expansion will focus on N'zoth, presumably as a nautical-based expansion involving Azshara and her Naga (and I'll throw in here that it should include Jaina Proudmoore's homeland of Kul Tiras and possibly the Zandalari with their sinking homeland, King Rakhastan, and mysterious prophet "Zul" - whom I've always suspected was some sort of Old God (or related thing) in humanoid form like Lovecraft's Nyarlathotep.)
So what do we know about N'Zoth? If this guy is really a master manipulator - to the extent that he could be manipulating the freaking Burning Legion - what is his bio?
Ok, first things first:
The Old Gods were created by the Void Lords, who themselves are paradoxical malevolent intelligences that exist within the Void. As Star Augur Etraeus refers, presumably, to them: "avatars of non-existence." Much like Sithis in the Elder Scrolls games, the Void Lords seem to want to eradicate existence. The Legion wants the universe to burn, but at least that would leave flames. The Void Lords want everything annihilated into pure darkness.
To do this, they want to create a Dark Titan (or Void Titan if you want to distinguish them better from Sargeras.) They want to take a Titan world-soul and corrupt it to their particularly pure form of evil, allowing said Titan to set about obliterating existence.
But because they are so utterly alien to our universe that they can't really exist within it, they sent the Old Gods. The Old Gods are basically darkness made manifest as matter. They sent the Old Gods into the Great Dark Beyond (the Warcraft name for just plain old Outer Space) to infect worlds.
There are presumably countless Old Gods out there - or at least there were before Sargeras started destroying worlds. But, unless Blizzard does a big retcon (and with this stuff made canon in Chronicle, I doubt they're eager to retcon this) Azeroth got hit with precisely four.
These were N'zoth, C'thun, Yogg-Saron, and Y'Shaarj. Their purpose was to function as a parasite on the planet, delving through the crust of the planet until they could pump the world-soul full of void magic. In the meantime, however, the Old Gods also created a number of races - or maybe not so much created as spawned. These were the N'raqi, Aqir, and C'thraxxi (possibly others.) The N'raqi are known as faceless ones, the C'Thraxxi are "faceless generals" like General Vezax in Ulduar, and the Aqir split into the Qiraji, Mantid, and Nerubians. (Ironically, you get quests from friendly Nerubians in Azjol-Nerub to fight against N'raqi, which either means that even races spawned directly from the Old Gods can resist them or it just means that this is an example of the established in-fighting between Old God-affiliated races.)
After subduing the Elemental Lords, the Old Gods had a kind of established pecking order. Y'Shaarj was the largest and most powerful, and Yogg-Saron and C'thun both submitted to its will. N'Zoth, on the other hand, was at the bottom of the heap. His armies clashed with those of Yogg-Saron and C'thun - and to be fair, some of this was just chaos for chaos' sake, but it really seems N'Zoth was kind of the pariah among the horrifying continent-sized shadow parasites.
When the Pantheon came to Azeroth, Aman'thul literally just leaned down and plucked Y'Shaarj from the surface of the planet - in terms of raw power, an Old God has nothing on a fully-fledged Titan. The major takeaway from that story is that the Titans realized simply doing the same with the other three could kill Azeroth, and with the exception of Sargeras, the Pantheon preferred keeping the patient alive over eradicating the disease.
But the other takeaway is that the biggest hinderance to N'zoth's power was taken off the board in a practically literal manner. Yes, C'thun and Yogg-Saron would both be threats to N'zoth, but they didn't have the kind of total domination advantage that they had with Y'Shaarj in charge.
And of course they were all put in Titan-made prisons (or really more containment, as it's not like the Titans could move the Old Gods.
But maybe that suited N'zoth just fine - perhaps some time away from its... siblings (?) would give it time to lay down some big plans.
After their imprisonment, the Old God who seemed to be hardest at work was Yogg-Saron. The death of the Pantheon saw the Keepers of Azeroth assaulted with incomprehensible new information - the last spark of the Titans' minds and souls were distributed to the Keepers. Loken took this particularly hard (in fact, only Ra actually understood that this meant the Pantheon had been killed, but everyone was kind of freaking out.) Yogg-Saron used this to goad Loken into an affair and then murder, which he then basically used to blackmail the Keeper into doing a number of things including implementing the Curse of Flesh. Yogg-Saron would also eventually use the reckless druidic works of Fandral Staghelm to infect the Emerald Dream with the Nightmare.
C'thun didn't do much other than send his Qiraji out to make war. But N'zoth also made a few plays. Some of these we don't explicitly know, but are merely strongly implied.
First off, N'zoth seems to be the one who corrupted Deathwing. While it's Yogg-Saron who shows us the vision of the creation of the Dragon Soul (which Deathwing would use to nearly wipe out the Blue Dragonflight among other things,) it seems more likely that it was N'zoth who did the corrupting. First off, Deathwing's home was in the Broken Isles, which is sort of around the border between Yogg-Saron's and N'zoth's territories (it's hard to tell given that the map in Chronicle that shows those territories is on a pre-Sundering Ancient Kalimdor.) But given that when Deathwing assaults Wyrmrest Temple, it's N'zoth's minons who are backing him up, it seems likely that the whole Deathwing plot was N'zoth's idea.
N'zoth is also probably the Old God who transformed Azshara and her closest highborne allies into Naga. While Yogg-Saron is up in the mountains of Northrend and C'thun is in the deserts of Kalimdor, N'zoth seems to be underwater in a place called Ny'alotha (which is presumably as bizarre and terrible a place as Lovecraft's Rl'yeh, the home of Cthulhu.) This suggests that he may have had another presence in Cataclysm as the benefactor to the Naga in Vashj'ir (providing them with his faceless minions.) In fact, we see a few utterly massive tentacles assaulting and corrupting L'ghorek toward the end of that zone's quests. It seems like it's got to be N'zoth doing that, which also suggests that his containment is seriously compromised.
One thing I don't totally understand but is definitely in the lore is the way that N'zoth took over the Emerald Nightmare from Yogg-Saron. Yogg-Saron explicitly introduced the corruption into the Dream, but for some reason N'zoth has been the one really implementing the Nightmare corruption. And with Xavius slain, according to Xal'atath (the sentient dagger that Shadow Priests use in Legion) N'zoth has now awoken.
But let's take another step back and really think about the situation we're in.
N'zoth warred against the other Old Gods. But Y'shaarj is long, long gone. And you know who else are? C'thun and Yogg-Saron. Ok, yes, granted, there's a lot of implication that when we "slew" those two Old Gods, we really just put them into comas/regeneration cycles.
But C'thun and Yogg-Saron must at least be at lower power levels than they were before we smashed their guts and brain respectively.
And that means that just as we're about to potentially unlock the gates on the prisons of the Old Gods (if my theories on the Pillars of Creation are right) it's going to be N'zoth and N'zoth alone who gets to take full advantage.
While the thoughts of the Old Gods are probably too bizarre and horrific to analyze their intentions, it does strike me if that if all this goes forward the way it looks like it will, N'zoth will emerge as the most powerful of the Old Gods, and perhaps as the most powerful being on the planet.