If you haven't watched Afterlives: Bastion, do so. It's on YouTube. You have no excuse.
Ok, done?
The Shadowlands are truly a plural set of realities - notably, when you journey to different zones in the expansion, the flight path takes you back to Oribos and then off again through a sort of waygate that takes you to a place called "The In-Between" before you reach the realm of the Shadowlands you'd been going to.
The cosmology of the Shadowlands is very different from what we've seen in the Warcraft cosmos up to this point. The whole saga of Old Gods, the Titans, and the Burning Legion is, for now at least, set aside for us to deal with things that we'd never seen before - the Eternals, which are sort of embodiments of the various realms as well as their leaders.
The four leveling zones each have their own Eternals leading them. Bastion has the Archon, Maldraxxus has the (seemingly absent) Primus, Ardenweald has the Winter Queen, and Revendreth has Sire Denatrhius.
Arguably, the Jailor fills the same role for the Maw, and its possible that the Arbiter is sort of that for Oribos.
So let's go down them one-by-one.
The Archon is a sort of archangel who rules over Bastion. The term Archon dates back to ancient Athens, and was used as a title for leaders of the city-state, which is fitting given the generally Hellenistic naming conventions in Bastion (notably, a lot of Christian terminology is based in Greek, such as terms like evangelist, episcopal, and even "Christ" itself, which is based on the Greek word "Christos," which was their translation of the Hebrew "meshiak" - aka "messiah," meaning "anointed one." In fact, Jesus as a name is just a Hellenization of Yeshua, which is the original version of the name Joshua.)
Having not yet completed any covenant campaigns, I don't know exactly how things will turn out with these characters, but while my initial viewing of the first Afterlives short made me question if the Archon was hiding something by dismissing Devos' concerns about the Maw runes carved on Frostmourne, Taliesin & Evitel's great (as usual) breakdown of the cinematic pointed out that, really, the Archon was just telling Devos herself not to pursue the matter, not that she wasn't going to look into it at all (though saying "Devos, your concerns are noted. This matter will be pursued, but you must return to your duties" would have probably been the better thing to say).
So far, thus, the Archon seems a bit distant.
The brainwashing elements of Bastion are one that I really want to explore further - if it's truly the annihilation of any previous identity, there's definitely a bit of a secretly dystopian aspect to the heavenly realm - sure, we don't want to be burdened by the sorrows of the past, but I, for one, would really prefer to remember my loved ones in the next life, especially given that the existence of an afterlife ought to mean I can see those loved ones again. On the other hand, it's also implied that one's memories are still preserved, and that perhaps a Kyrian can revisit them, but with a safe distance between them and the trauma they suffered in life, being able to view it as a record, rather than reliving it as a memory.
The Archon doesn't play a huge role at least in the leveling quests. So let's move on to Maldraxxus.
The leader of Maldraxxus is a being known as the Primus. And he's totally missing, as far as we know. Where he has gone, I don't really know, but his coordinating hold over the five houses has clearly crumbled. Maldraxxus is in total disarray when you get there, and one senses that the strong hand of the Primus kept the place functional.
But you, the Maw Walker (get used to hearing that like you heard "Commander" in Warlords,) discover a rune blade left behind by the Primus, seemingly for you to put down the traitors of Maldraxxus and restore the Undying Army to its rightful place as the Shadowlands' defense force.
Maldraxxus is odd because while it's super gross and seems like a kind of terrible place to wind up, it's actually one of the "good" afterlives. This is the place where the eternal warriors wind up - basically, the most badass soldiers in life, those who are always up for a fight, are selected to become the defense force for the Shadowlands. And there are actually three familiar figures we encounter that are part of this afterlife from our journeys in Azeroth (well, and Outland.)
Bearing the strongest resemblance to the Scourge, it's hard to recontextualize the Maldraxxi as good guys (though given the drama going on, in fact most of the surviving ones are bad guys at this point) and so I really have to wonder what the Primus is like in person, and not as disembodied whispers from his giant skull-headed seat at one end of the zone (I assume the giant skull-face is a statue of him, and not the Primus himself.)
Ardenweald is ruled over by the Night Fae, and I think what's striking about Ardenweald is that it feels the least like an actual afterlife. Which is appropriate, as it's more of an "interlife." The whole point of Ardenweald is to let dead nature spirits recuperate and regenerate before they are reborn into the world. We know that Cenarius went here after Grom killed him, which is how he was able to come back in Cataclysm.
The Winter Queen is the leader of the Night Fae, and as far as I can tell, she's a leader that we can more or less just trust (which is shocking, given that she's explicitly identified as Fae.) Ardenweald is suffering a great deal from the Anima drought, which has forced them to actually let some of the groves where nature spirits regenerate in Wildseeds to wither and die permanently. Just as the zone itself has its resources stretched out over the realm, the problem you face trying to speak with the Winter Queen in the quests here is that she is also stretched too thin, appearing only for moments when you first have your audience with her - without enough time to talk about anything.
Finally, we come to Sire Denathrius. It should come as no surprise that Denathrius turns out to be a bad guy, given that we already know he's the final boss of the first raid. Revendreth is, itself, very different from the other realms we encounter. While the other three are theoretically good places to find yourself when you die (though again, I think I'm just very definitely not the personality that would be happy to wind up in Maldraxxus) Revendreth is explicitly the second-worst place to turn up in the Shadowlands.
Revendreth is basically purgatory - your last stop to try to atone before they dump you in the Maw for all eternity. The methods the Venthyr use are pretty draconian, hunting them through a spooky forest, locking them away in crypt-like chambers for centuries, and generally just making things miserable for them.
But the good Venthyr of this realm stress that the ultimate goal is rehabilitation. Anyone who is a Venthyr was first sent here, meaning everyone here lived a life of monstrous crimes - the scale of which suggest that even someone like Gul'dan might be sent here rather than directly to the Maw (T&E in that same linked video speculate that the way it's supposed to work is that absolutely no one is supposed to go directly to the Maw - that you only go there if the Venthyr can't drag you kicking and screaming to salvation.) It makes Uther's punishment of Arthas feel that much more unjust - given that Arthas, while a rotten bastard, is definitely not the worst person in the Warcraft cosmos (and his soullessness during his most heinous acts is one hell of an extenuating circumstance.)
Anyway, Sire Denathrius is actually the most personable and affable of the Eternals we meet during our questing, welcoming us to his realm and eagerly thanking us for our help - at least until we find out that he's been hoarding anima and thus probably working with the Jailor.
Thus, this is the most high-profile traitor we know of, and which also means that if we are to restore the Shadowlands to its proper order, we'll need to somehow replace him (Prince Renathal, who I think is very intentionally meant to seem like Alucard from Castlevania, is the obvious choice to do so.)
How long Denathrius has been betraying his purpose is a good question, but under him, the Venthyr have taken to torturing souls not to save them, but to drain every last drop of anima out of them, and also to just kind of get off on the sadism.
There's a region of Revendreth that introduces familiar cosmic forces in really interesting ways called the Ember Ward. Here, the Light (not just light, but The Light) beats down upon the earth, scorching it and draining the energy of any venthyr who wind up here - while they can't die from it, they do seem to be driven mad by it, not unlike the Wretched or Withered. The aversion to the Light is obviously a reference to the Venthyrs' similarities to vampires, but it also opens up new story possibilities for us to really figure out how all the new stuff of the Shadowlands fits into the existing Warcraft cosmos.
Denathrius based the Venthyr on his own form, even though he doesn't totally look like them, but I really wonder, then, what his origins are.
The very idea that these entities are called Eternals suggests that they have sort of always existed. But I wonder how true that is. I'm not the first to point out that Denathrius, and his Castle Nathria, and the gothic nature of Revendreth, evokes the Nathrezim, those particularly important demons also known as Dreadlords whose trafficking with the void and the Old Gods (not the Old Gods we're familiar with, but at the Titan world Telogrus) was what drove Sargeras to embark on his universe-culling Burning Crusade.
We know there's a planet called Nathreza, which would seem to be their homeworld (though I remember maybe an earlier theory that they were from Xorroth) but I also really wonder if they have anything to do with Revendreth and Sire Denathrius - either they could be escaped and twisted Venthyr or Stoneborn, or perhaps Denathrius was actually a Nathrezim who somehow got the job of running a realm of the Shadowlands.
Or maybe it's just a coincidence? But that would seem too easy.
Rather than going into the Jailor and the Arbiter, I think I want to touch briefly on (there's room for a whole other post in this topic) the connection between the Shadowlands, the Burning Legion, and the Scourge.
Up until the announcement of Shadowlands, our explanation for the Scourge was simple - just demonic magic, only with an icy blue vibe instead of a burning green one. We were told that Kil'jaeden turned Ner'zhul into the Lich King, and that was how we got the Scourge. Simple as that.
But while it is definitely new lore (which doesn't necessarily mean a retcon!) we're now discovering a whole other plane of reality from which the Scourge drew its power.
We knew from Blizzcon last year that the Scourge got its forces (or at least a lot of its tactics and ideas) from Maldraxxus, which makes sense given the abomination-like constructs, the virulent plagues, and such. But we're also now really learning that Frostmourne and the Armor of Domination (if that's what it was called - the Helmet seems to be the real operative part) have runes from the Maw, and we know that we're going to be crafting legendaries using that same magic (always us with the super-dangerous magic!)
The Jailor must have been aware, if not complicit, in this happening. But I also really wonder how Kil'jaeden pulled this off.
Kil'jaeden, while a formal mortal, by the time he made the Lich King, was one of the most powerful demons in existence, basically sharing a number two slot with Archimonde (or a number one slot if Sargeras never technically counted.) We're told that no one has ever in all of history escaped the Maw before we did, though I suspect we're going to find out that this isn't actually true.
Was being one of the most powerful demons in the universe enough to let Kil'jaeden journey to the Maw and take some its power to create the Scourge?
I feel like the implication is that even for Kil'jaeden, that'd be a real feat.
I mean, to what extent did the Burning Legion understand the Shadowlands?
Yeah, this is a whole other post. Better wrap this one up.