Alright, I'm going to take a shot at the Karag Dum-Morghur mystery, so this post is going to be long:
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.
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:
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.
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.
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.
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.
