Alright, I'm going to take a shot at the Karag Dum-Morghur mystery, so this post is going to be long:
"'Runelord' is the title Thungni bestowed upon the son that succeeded Him when He departed," he explains patiently. "Those that oppose Karag Dum's Runesmiths say that to declare that insufficient is to say that they have reached heights that one taught by Thungni Himself could not reach."
"So it's something of a religious schism."
"And a Clan feud, and a Guild dispute. That is the foundation of the conflict, but not the climax of it. In the Runesmith Conclave of 6769, the last that Karag Dum attended, they announced that Chaos was waxing and that all efforts needed to be spent preparing to withstand it. This was taken poorly, seen as an attempt for Karag Dum to increase their status. Karag Dum has always been focused entirely on the threat of Chaos and has always called for more efforts spent to oppose it, so this was seen as their usual rhetoric, only more so."
You make the mental conversion to the Imperial Calendar - 2246 - and you're pretty sure you know where this is going. "But it wasn't. They were right."
Thorek sighs. "It is easy to see that now. But from what I've been told - and it seems to be true - that century was a tumultuous time in the Old World. High King Alrik had died in battle at the Battle of Black Falls, Bretonnia was tearing itself apart over succession, humans marched on Nehekhara time and time again and agitated the Tomb Kings into a great deal of activity beyond their borders. Worst of all, at the time of the Conclave Ulthuan's forces were on the march in the Old World. In the face of all that, it seemed very self-serving for Karag Dum to announce that it was Chaos that was the real threat. A great deal was said in hot blood, every word of it recorded for posterity."
"What were the Elves doing?"
"Pursuing the Beastman demigod Cor-Dum, but that was not known at the time. The Phoenix King Finubar was still new to the throne, and many Dwarves suspected the worst when his forces made landfall in the Old World."
So this is the first big hint as to what is happening that I will be dissecting. Note here that the last Runesmith Conclave Karag Dum attended was in 2246. This date is important because of something Joerg says later. The warnings that Dum gave were ignored because of the High King's death at the time, Bretonnia tearing itself apart, the Tomb Kings stirring, and Ulthuan landing at the shores of the Old World. It is explained that Finubar wanted to rebuild bridges, and I will be going over this in more detail later, but the Tomb Kings and Ulthuan landing, and the date of the conclave, 2246 is what I want to highlight.
"I'm not an expert on Runes or Beastmen, but it seems clear they've used some sort of Runecraft to bind Morghur to their service. Perhaps some sort of illusion or ensorcellation, perhaps something to burn the Chaos taint off of him to free him from the orders of the Chaos Gods. Perhaps his latest incarnation was born to Dwarves, and they managed to either bind him or protect him or raise him so that he's more loyal to them than to Chaos. I don't know if Morghur's been sighted in the Old World since the Great War Against Chaos-"
"Not since the Battle of Arden in 2244," Sir Joerg says.
Joerg here says that the last time that Morghur was spotted in the Old World was in the Battle of Arden in 2244, the reason Ulthuan landed on the coasts of the Old World and one of the reasons the Dwarves ignored Dum's warnings in the Conclave that happened in 2246 two years later. This is how Asarnil describes the Battle of Arden:
"I wasn't a part of that jaunt, but three of my cousins were," Asarnil says. "Finubar's attempt at building bridges. The Forest of Arden had been corrupted by Morghur and Beastmen flocked to it from across the Old World. L'Anguille called for aid against a foe they could not understand, the Everqueen pushed for its restoration, and the so-called 'Glade Lord' Araloth that was preparing a great hunt for the beast had a lineage greater than that of some Princes. Finubar the Haggler saw a chance to earn credit with three polities at once, and was all too eager to spill Elven blood for it, so Prince Eldyr of Taranoc and Handmaiden Ystranna raised a mighty host. Many of them never returned." Asarnil chuckles darkly. "Bitterness over that poisoned any hope of improved relations between Ulthuan and its abandoned colony, the Bretonnians gave all credit to their Lady, and as for the Everqueen, it wasn't long after that she found she much preferred the brother of your Teclis than the company of the Phoenix King. Finubar has a gift for snatching defeat from the jaws of victory."
Yes this is a biased account, but it's the most detail we get on the actual Battle of Arden, the last time Morghur was sighted. Asarnil never mentioned if Morghur escaped or was "killed" in this confrontation, but the implication is that they technically won even if they suffered a lot of losses. So we know that Morghur was last sighted in the Forest of Arden in 2244, the Dum reps arrive to the Conclave in 2246, they get ignored and some time later Morghur ends up at Karag Dum. The expansion rate of the sands at 6 inches per day means that the area of the sands roughly lines up with around 2 centuries of expansion. This implies Morghur ended up in Karag Dum somewhere after 2246, if he indeed has a connection to the sands.
The mostly flat landscape starts to grow rugged as you approach the foothills of Karag Dum, and nervousness gives way to anticipation in the atmosphere of the steam-wagons. You stay quiet, occupied with the dark mutterings you heard from numerous sources about what fates might have befallen Karag Dum, and what lengths they might have gone to to avoid them. The temperature has been steadily falling as you ventured further north, but here it grows hotter and drier as the ascent continues. You pass tattered banners hammered into the bare stone of more varieties than you can identify, most seemingly Kurgan, some completely unfamiliar to you, and others completely wiped clean by the hot, gritty wind that seems to be blowing directly into your face. And then the Alriksson crests a final rise and the landscape opens up before you, and you barely manage to release the Rite before shock tears it from your grasp.
You'd seen pictures of Karag Dum, the tallest of a small cluster of mountains approached through an exposed vale. But now it stands alone, jutting out from a great crater that you find yourself on the lip of. Directly below you is bone-white sand, interrupted regularly by actual bones that grow thicker on the ground the closer it is to Karag Dum. And with shocking abruptness the desert gives way to disturbingly familiar forest that now rings the base of Karag Dum, burying the bottom third of it in apparently primeval forest that by all accounts was not there a mere two centuries ago. And as you stare and as the Alriksson continues trundling forward, you see a figure at the edge of the forest, standing taller than a man and taller still when you consider the skull-adorned frill that juts from its skull.
This is a description of Karag Dum as it is now, and I'm quoting it mostly as a reference for people to know what it looks like. It's a crater filled in with white sand strewn with bone until it breaks into a primeval "familiar" forest that transitions into a singular mountain, rather than being the largest of a series of mountains extending from an exposed vale.
"They're definitely Old World species," Journeyman Cyrston says, peering through a telescope. "I'd need to get up close and collect seeds and samples and bring my own Magesight to bear to say with any certainty, but if I had to guess, I'd say northern. Drakwald, Laurelorn, or Forest of Shadows."
"Any idea how it would have got here?"
"Apart from just labelling it Chaos Waste weirdness? None whatsoever. Until I clapped eyes on these I'd have bet good money you wouldn't see any of these species further north than the Western Oblast."
"And their age?"
"Under normal circumstances, which," he gestures vaguely at the Chaos Wastes behind you, "I'd say it would take centuries undisturbed, perhaps longer. These are old forests. The type you don't go into lightly, because if there's not something terrible already living there, it's because the trees are the something terrible."
"Any sign of mutation?"
"Nothing major. Though I can't rule out minor mutations at this distance."
Here Cyrston uses the term "Old World Species, Northern". He then uses Forests from the Empire such as Laurelorn, Forest of Shadows and Drakwald as examples. The question is, has Cyrston been to Bretonnia? The Forest of Arden, which used to be the lair of Morghur and the last place he was seen in, is also in Northern Bretonnia, which is also in the Old World. The Forest of Arden is roughly level with Laurelorn/Forest of Shadows but is simply farther west as a result of being in Bretonnia, so it strikes me as likely that the Forest was plucked out from Arden.
"Dormant stratovolcano," says the Dwarf that Snorri fetched for you as soon as you ask about Karag Dum.
"And the stone of the landscape around it?" you ask, still staring at the edge. "Don't answer from memory, look at it and tell me what it is as if you'd never heard of this place before."
He obeys, producing a pickaxe from his belt to chip off a piece to examine, and then carefully chew. "Scoria," he says with confidence.
"Is that what should be here?"
"Aye. More mafic than I'd have expected, but then again, we are far from the mountains I know."
"And the sand? Is it fragmented scoria?"
"No," he says instantly. "Wrong colour completely." He bends down and picks some up, letting it run through his fingers before putting a pinch in his mouth. "Sedimentary silicate, not igneous. Nearest place you'd find this is the southern Dark Lands."
You remember what Cyrston said. "Anywhere in the northern Empire with that sort of sand?"
"Nowhere near. All I know of that would is the southern Dark Lands, Araby, and Nehekhara."
With a tiny fizzle of Divine energy, a tiny piece of rock disappears from the lip of the crater, replaced by a few grains of sand that tumble down to join the rest of the desert.
This part is hard for me, as I'm not good at geology. That being said, from my research, a "stratovolcano" seems to be a type of mountain built from Oceanic and Continental Crust subduction zones. These type of structures also tend to be heavier in Fesic than Mafic, which the Dwarf noted here as not necessarily being the case. As far as I know there are no oceans in the areas surrounding Karag Dum, so the construction of a stratovolcano here seems weird. The Dwarf here also mentions that the sand is not fragmented scoria, despite the presence of scoria around the crater, but rather sedimentary silicate, the kind you'd find in the Southern Dark Lands, Araby and Nehekhara.
The area inside the crater is hotter and drier than the area outside it. Stone that enters the area is transmuted into white sand of a sedimentary silicate nature with time, and other objects are buried inside but not impossible to pull up. Skeletons don't get buried, instead floating to the surface through some buoyancy. Despite there being no time dilation effect on the spoilage of an apple, bodies that fall in the crater are skeletonised far quicker, ending up as skeletons after one day. The sands expand past the crater at a rate of 6 inches per day. The ambient Dhar in the area is lower than the surrounding areas, and described by the Lights as maintaining a steady frequency, going no higher or lower. The ambient Dhar is still higher than non Chaos Waste area. There is some sort of divine energy responsible for transmuting the sand, not one that Mathilde recognises but not Chaotic in nature. Morghur's chaos aura is somehow surpressed while he's in the area, only being shoved out when he's threated.
The Beastmen come from the forests, and they only partially feed on the bodies and leave them. This behavior is what they do when they're wary and being defensive, protecting something sacred to them and expecting counter strikes. How do the Beastmen come in? Joerg provides the theory that they're using the "Beast Paths". My current theory on what the beast paths are is that they are a corrupted version of the Asrai's "World Root" movement system allowing them to walk between trees. My theory is that the forest the beastmen are surrounded by is a portion of the Forest of Arden plucked out of Bretonnia and shoved in here, and there are Beast Paths leading from Arden to this portion of the Forest.
I don't have a definitive answer, but I think what Thorek said up there is a clue. Around the time that Dum was warning of Chaos, the Tomb Kings were stirring and Ulthuan landed on the shores to deal with Morghur. What if Dum saw the threats encroaching on the Karaz Ankor, they saw Chaos, and they decided to deal with multiple birds using one stone? They must have had some space manipulaton/communication/translocation runes, but my theory is that if we go to the Forest of Arden in Bretonnia, perhaps in Artois, perhaps in L'Anguille, perhaps in Gisoreux or even Lyonesse, we might be able to get more info on this line of inquiry. The Tomb Kings are a far more difficult line to pursue.