Mithral, also known as "Truemetal" among the Dwarf smiths, was a precious metal produced from ore found in the Underdark as well as mountain ranges in certain areas. Especially prevalent in the central Crowncrests, mithral ore appeared as a silver-and-black mineral in its natural form, and became a shining silvery-blue when it was forged.
Items cast from mithral weighed only half as much as similar items forged from steel. Since pieces of armor made from this valuable metal were very light, they allowed the wearer to make better use of their natural agility, and were less restrictive on Spellcasting.