Tantalum is a rare, blue-grey metal that is found deep within the chasms of Ferchiun*. Immune to all but the strongest acids, if more had heard of it would be more sought after. It is nearly as hard as adamantine and holds an edge equally as well. Those few who believed such a tale did not return from their quest to gather any, or if they did, it was not to the homes from which they came.
These creatures are foul things that prey on the weakness of loss. Their home society, and indeed, their home, in completely unknown, as all that have been found have been killed to out standards.
The World is actually a number of continents surrounded by oceans, which are in turn surrounded by mountains. The oceans rush off the edge of the plateau on which the World sits into the Outside...