Voldstal

A metal that few cultures are even aware of, volstal - literally "awe steel" - or the "Flesh of the Father" in the The Grey Tongue, this material is the kind of all metals; however, another name for the material - "The Unforgeable" - highlights while this material is hardly utilized. With a glass-like composition upon cooling, this metal possesses an impossible sharp edge. No matter the level of detail, there are no serrations or imperfections in the blade. It is also the hardest metal known - not breaking even upon contact with adamantine. Even spells that heat most metals to furnace like temperatures have no effect on this legendary resource.
To date, only a handful of individuals have managed to acquire the knowledge of the process used to form this substance into any useful shape. Volstal is a seductive material in that blades formed of it are able to slice through steel, splinter mithral, and even chip adamantine while being fractions of the weight of those lesser materials, The requirements to forge with it are dispensed only by Gho’bainn: The Maker and the path is long and arduous indeed to acquire the necessary tools, resources, and reagents to provide the necessary conditions. To work with volstal, an appreciable quantity of the material must first be located which is difficult in its own right. Legend holds that deposits of the substance can be located immediately by a mature dragon of the line of Alzairu'Arima; of course, rumour also holds that such a creature is capable of smithing the material via their magic of Sintergy. Once an amount is located, it is mined easily enough as the process required to shape it eliminates any rock or other solids contained in the ore.
From this point, the smith must obtain a crucible formed of diamond which must be enchanted with resistances to heat. The diamond crucible must be able to withstand hellish temperatures while not fracturing. Upon having obtained a suitable vessel, a forge must be constructed that is capable of generating temperatures in excess of 4500 degrees Celsius. The crystallized soul of an elder fire elemental will do. For the layman, an elder fire elemental is something like a phoenix. Generating the heat to liquify the metal for require all of this being's energy; therefore, a new fuel source must be found for each individual forging. Once the metal has been heated and the heat source extinguished, there remains precious seconds to dispense the material into a special mold.
The mold must be carefully constructed to be as correct as possible especially for the portion that will form the blade. Volstal is nigh impossible to sharpen. Even utilize Shardscale Powder whetstones, it would take decades to refine the edge on a volstal blade - to say nothing of profiling a billet into a suitable form. Additionally, the substance must be capable of absorbinb the star-like temperatures of the liquid metal without shattering before it has solidified. The ideal material is glacial ice taken from a Melt Worm tunnel. The passage of such a creature does imbue the melted deep ice with a resistance to heat. This is an excellent starting point. The material must then be enchanted - shocking, I know - with three feathers from The Winter Congress and the heart of an ancient dragon of the frost or white varieties. Once the blade is forged, it should only require touching up once every few centuries if you've done your job well.
It would also be advised that you possess some means of withstanding the appaling temperatures associated with these processes and reagents else you turn into a pile of slag.

Type

Metal