May I interest you in my custom composite theory I posted a while back?
[] THEORY: The specifics are hazy, but this is a known contingency plan that Borek is entirely aware of, but hoped hadn't been enacted. The result breaks all Dawi notions of acceptability, but Karak Dum survives in some capacity and continues to inflict attrition on every local and visiting Chaos force that want to take a swing at them, so it is considered a lesser evil by the pragmatic Karak Dum. From their extensive study of Chaos, they had previously figured out how to deliberately induce Morghur's reincarnation into a specific body, even that of a dwarf. To contain and control Morghur after his induced reincarnation, the Dwarves of Karag Dum did something to burn away the taint of Chaos, much as your Belt of the Unshackled Mountain does, but on a far grander scale. Burning out the taint of a demigod named "the Corruptor" is likely why there's a desert and fewer mountains here. The forest was created by the purified Morghur, and the beastmen were attracted to serve him as they are inherently bound to do. The rulers of Karag Dum would not force such a fate onto any of their subjects, so this "Morghur" was likely a member of the royal clan who was pre-selected in case this contingency needed to be activated, and was personally known and loved by Borek, explaining the greeting and his reaction to it.