Simply put: A rare and powerful Alloy. D-steel is very light weight but has a very high impact and stress tolerance level, and by most people is considered indestructable, but this is highly doubted. Titanium was once thought to be indestructable...
So far however, the metal hasn't been proven to show any sign of weakening under testing. The metal is hard to find, being a synthetic alloy created by a Dr. Khiten, the only one who knows how to create the metal. D-steel is very sparsely found in distribution and cannot be reforged into another shape. What you find is what you get.
D-steel is a very shiny, lusterous metal, reflecting light much in the same manor that a gemstone would, thus its name was given. It is this same quality that makes it very valuable, not for its appearance, but for its properties of refracting and repelling all forms of energy (including heat to a certain degree). This makes D-steel is ideal for armor and shields because it makes the wearer invulnerable to energy attacks. D-steel is a poor conductor and is not readily attracted to magnets.
Another unusually noted quality of this metal is its ability to cool rapidly. D-steel ices over quickly in cold temperatures. Under these conditions, D-steel is not suggested for use as armor or for other defensive purposes. While D-steel is unaffected at any temperature, a reploid using D-steel armor in cold temperatures would have a very hard time keeping its temperature level high enough to operate. They would freeze easily, rapidly, and/or possibly permanently.
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