Morkjarn, Dark Iron

Morkjarn is a black metal found deep beneath Svartalfheim. It is the material most Svartalfheim Dark Elves make their alloys for their weapons and armor from.
It was found far below the surface of the realm about one millennia ago. When discovered, it turned all of the dwarves under the caves of Svartalfheim into Dark Dwarfs and changed their souls to be greedy for the metal.
The Dark Elves soon realized these new Dark Dwarves could be controlled by feeding them tiny bits of the Dark Iron. By doing so the Dark Elves sealed themselves into their fate: supply the Dark Dwarves with the black metal or suffer an uprising.
By following this deadly cycle, their entire culture has become based on the supply and demand of the metal, much more than the other gems and metals coming from the caves.
These days the metal can be found in all nine realms because of trade and strife.

Tip

The material is worth far more than gold or silver, attempting to steal some may be a bad idea.