[@Serpentine88]Wanna buy mithril?
Even if you don't I think mithral-derived products would be essential for your nation. You need something which can take the pressure yet also light enough to be worn by your people. Mithril's steel-like properties yet density third of steel would be ideal for this.
But well, given Yllendthr's near monopoly on mithril it's going to be really expensive, especially since you can't just melt it to other forms after use.
Mithral (precursor element of mithril) is a cheaper but also inferior alternative which you can actually produce just like one does steel. It's more commonly used as ingredient for white paint, though.