Of the stories in Legion, I suspect that the one of the Drogbar and Dargrul's theft of the Hammer of Khaz'goroth is probably one we're not going to be revisiting any time soon. We have, I think, quests coming up to tie up the story of Odyn and Helya in Stormheim. We've had the Emerald Nightmare serving as a serious climax to the stories in Val'sharah. We've had and are getting weekly updates on the story of Suramar and the Nighthold. And Azsuna's story might be wrapped up, but Azshara remains a presence in the world that we'll have to deal with at some point - whether as a raid boss or the headliner for an entire expansion, who knows?
But Highmountain's story is probably done. We had a once-cooperative group of people who fell apart. Dargrul rejected the idea of giving the Hammer to outsiders (the player characters and our compatriots) and so he stole it apparently to keep it safe. The Bloodtotem reacted to this loss of unity by selling out to the Burning Legion, and we dealt with both groups pretty definitively in the Highmountain quests.
But there's something that has been bothering me about all of this, and it's Highmountain's absent player: Deathwing.
Obviously Deathwing is over and dealt with - we not only killed him at the end of Cataclysm, but apparently did a massive "all timelines intersect here" spell (well, Nozdormu did) to ensure that Deathwing couldn't survive through the manipulation of the timeline (to be fair, this isn't entirely explicit, but if you beat Madness of Deathwing and Nozdormu gives the little speech before firing the Dragon Soul, he more or less says this is what he's doing.)
Deathwing was once a good guy, granted power by the Keepers to guard over the deep places of the world. He was well-liked - trusted by Alexstrasza and close friends with Malygos. This was back when he was called Neltharion.
The thing is, spending so much time deep below the earth, he was closest to the prisons of the Old Gods, and they were able to slowly, gradually get into his head and begin to corrupt him. Eventually, the corruption manifested physically, as Deathwing's primal fury threatened to erupt out of his body. He had to get metal plates attached to his body just to keep him from blowing apart, and the corruption spread through his entire dragonflight.
And where was it that this corruption happened? Well, we don't know for sure. Presumably it was a slow and gradual process, and one would imagine that the place Neltharion spent most of his time was his own home - in other words, Neltharion's Lair.
So right inside the core of Highmountain is where Neltharion was corrupted by the whispers of the Old Gods.
While it was the goblins who were tasked with applying the plates that covered his body, it was the drogbar who fashioned those plates, and Deathwing kept the drogbar in his lair as slaves to force them to do this labor. After Deathwing departed, the drogbar kept the lair as their own capital city, and it is from there that Dargrul ruled over his clans.
In Highmountain, the Highmountain Tauren often caution you to "beware the deep places of the earth." Often when drogbar attack, they shout "darkness gonna take you!" We even find a vignette enemy in a cave (this one populated by kobolds) that is a void-walker like being, who is summoned by blowing out several candles.
Isn't it possible, or indeed likely, that Dargrul's mind was being manipulated by the Old Gods? Dargrul is often referred to as the "mad king" during quests in Highmountain, and who is better at driving people to madness than the Old Gods?
Dargrul's actions drive a once-united Highmountain into deadly conflict and war, which certainly seems like the Old Gods' MO.
But is this chaos enough to motivate the Old Gods?
I've talked before about a theory surrounding the Pillars of Creation - specifically that while they might successfully seal the portal that is allowing the Legion to invade, they might simultaneously unlock the prisons holding the Old Gods captive.
The theory is that this invasion was actually orchestrated by the Old Gods through extraordinarily complex means that I described in that earlier post.
But doesn't this contradict that theory? Why would the Old Gods drive Dargrul to steal the Hammer if they really wanted us to use it in conjunction with the other four pillars to crack open their prisons? It would seem that taking the Hammer would impede that plan, and it would be better to just let us take it from Thunder Totem.
But that's assuming that using them as intended would release the Old Gods.
Perhaps instead they needed to introduce a flaw into the system. Just as the Curse of Flesh was essentially a computer virus uploaded into the Forge of Wills, perhaps there is a flaw that the Old Gods needed to introduce into one of the Pillars before they could be used.
All we know of what happened with the Hammer of Khaz'goroth while it was under Dargrul's control is that he went mad with power and learned he could smash entire villages into smithereens. But what if while the Old Gods were driving Dargrul's bloodlust up, they were also subtly and carefully recalibrating the Hammer to do what they needed to do?
Dargrul's aggression would be sure to draw the attention of the heroes of Azeroth - the ones they expected to use the Pillars of Creation.
And now, the Hammer of Khaz'goroth sits in Dalaran like a bomb waiting to go off, possibly spreading its new flaw into the other four pillars all the while.