In my Norsca campaign, the party of norsca characters is currently in the town Gardariborg. Just south of this city, there is a ruin of a dwarf hold marked "Kraka Ungrim, The Foul Fortress".
Here is the sparse fluff I have found about this place:
The Norse Dwarfs establish new outpost called Kraka-Azkahr, which could be translated as the Fortress City. Site has rich veins. Only problem is very aggressive neighbours (the Vargs, the Trolls and the Ogres) and that the new outpost is not protected by the magical Dwarfen Stones (Dwarf year 5100)."
The Dwarf stronghold/outpost of Kraka-Azkahr is overrun by the Chaos Horde sent by the Valmir Aesling, the Emperor of Chaos, and his Varg allies (Dwarf year c.5300).
The Imperial Dwarfs help the Norse Dwarfs to create expedition to travel the lost outpost of Kraka-Azkahr. They found ruined outpost full of foul creatures of the darkness. Small tribe of the Chaos Ogres are now living in the upper levels of the hold. Lower levels have Chaos Trolls and other foul creatures. The Hold is lost and the Dwarfs probably killed. The Imperial Dwarfs give the place new name - Karak-Ungrim (the Foul Fortress), which becomes Kraka-Ungrim for the Norse Dwarfs. The Dwarfs leave the hold and try to forget this dark place. But there are strange rumours after this about the fallen hold. Rumours about horribly mutated Chaos Dwarfs (Dwarf year 5304).
Now, there is a chance that the characters will try to explore the depths of this fortress looking for a mcguffin, so I was wondering if anyone got any inspirations from the text above about what they might encounter.
The obvious answer is Chaos Dwarfs. However, CDs are not just "evil dwarfs". They are a specific dwarf culture situated in one specific location that was corrupted by worshipping Hastur.
These dwarfs seem to be a separate case however. So what has happened to them while living isolated deep below ground in the mountains of Norsca?