What is mithiril? Silver based alloy with strength of steel and 1/10th the weight, made by the elves from a fallen star that landed in lake Glitter Light. No more is to be found. There are still items made from it, almost all in Ynth. The dwarves of Vegas Deep found a small vein once and pursued it deeper into the earth than anything else they had ever done – but it played out and only a few weapons exist in the north that were made from iot.
Making items from it required a process that saw a great deal of waste and super high temperatures. For each pound of viable material, there may have been 50 of waste that was not pure enough.