Magic Items
Adamantium
Black and non-metallic, Adamantium is the hardest known substance on Mundus. Adamantium seems to drink in the light, and is non-reactive to both fire and acid. Adamantium is highly prized for it's lightness and durability, and can only be worked by Artificers.
Weapons made of Adamantium cause Critical Hits on a roll of 19 or 20.
Armor made of Adamantium is half the weight, and the wearer is immune to Critical Hits.