Obsidian

A pitch-black material that is considered virtually unbreakable. Extremely rare and valuable, the only way to change its shape in order to fashion weapons, armour and other objects out of it is by using the Arts.

Obsidian can be set ablaze with fire, and it will keep burning indefinitely without getting damaged, until the flames are somehow extinguished. It's therefore especially sought after by fire elementals for weapons to channel their powers through.

Two such examples are Surtur's sword the Souleater, and the weapon used by the mortal Wanderer against Arúmil while having lost his powers.

There exist two artificially modified variants: neo-obsidian and meta-obsidian.