Magic steel is not simply valuable just because of its rarity. The true reason behind its worth, is because the metal possesses the property of an extremely good affinity with guiding magic power. It is possible to control magic essence to a certain degree using your imagination.
Even though demonic steel is excellent against demonic abilities, it, as every other metal, has a melting point. The melting point for most rare resources is around 5,000 degress. Demonic steel can withstand temperatures up to 9,900 degrees. Furthermore, it can regenerate.
It is invaluable for production of mounted soldiers’ weapons. Since it can change shape at will, it’s useful for receiving and dealing various attacks, to say nothing of carrying it.