Adamantium is a magical material discovered during the Mage Wars. It resembles steel but is an element by itself. It is a powerful magical amplifier and is much sought-after. It soaks up energy like a sponge, and when enough power is absorbed, it amplifies as it drains, like a capacitor, in the presence of Mithrill.
During the Mage Wars, Adamantium was fairly rare, but common enough that entire towers were sometimes clad in it. During the Second Chaotic Period, much of the adamantium was lost, destroyed, or stolen by dragons, increasing its scarcity. While reserves have never been catalogued, there is estimated roughly 200,000 tons in the Known Worlds.