Warning: This definition may contain spoilers from any number of Games Workshop novels or source books.
Karak-Varn: Karak-Varn (Kh. lit. "Stronghold of Lake Enclosed by Mountains) is one of two dwarf holds which over-look the Black Water, at the jucntion of the Black Mountains and the World's Edge range. It is commonly known to most Older Worlders as "Crag Mere" because of its position above the western cliffs of Black Water lake. The nature of the Black Water crater made the perfect location for the Dwarfs to mine Gromril - the star-iron which dwarfs used to forge legendarily solid armour and razor-sharp weapons. Like Karak-Ungor before, the Dwarfs mines were their own downfall: as they mined deeper into the cliff-face for the prized Gromril, they rached so deep that their tunnels touched the underground waters of the lake. This made the whole foundation of the hold unstable. When that part of the mountains was struck by one of the earthquakes which are common to that part of the world, the Black Water rushed into the tunnels, galleries and workings, washing away thousands of dwarfs and tonnes of their treasure.
This was just the beginning. For the long years since its construction, Karak-Varn had been regarded with envious eyes by the Skaven, for similar reasons to those which had brought the dwarfs to it in the first place. Whilst the dwarfs treasured gromril, the Skaven lusted for the warpstone which had been laid down in the same way. They boiled up through the wrecked tunnels with goblinoid allies, driving the dwarfs from their ruined hold even as they struggled to shore up the damage. The taint of warpstone spread through the city, and no dwarf would willingly live there, even if the things which lurk within were driven from it.
So why would any dwarf go back to Karak-Varn? For Gromril - expeditions frequently brave the terror of the dark beneath Karak-Varn for the remnants of the Gromril still to be found in the deeper passages. Engineer have built many cunning devices to enable the Dwarfs to probe the depths, even those underwater, where the richest and as yet unplumbed workings can be found. This dangerous work, to say the least. The Skaven still dwell in Karak-Varn, and worse things too. The Truly Dead Vampire Wietzak makes his lair here, ruling over many of the creatures which share the darkness with him.