Sulfuras is the mighty weapon of Ragnaros the Firelord. The weapon never leaves his grasp. It is composed of flaming red elementium and etched from end to end with intricate runes that seem to move like flowing lava across the weapons surface. Sulfuras is covered with many vicious pikes of varying sizes, each white hot and surrounded by the distortion of shimmering heat.
When a creature is slain by Sulfuras, its body is consumed by intense flame and effectively disintegrated, leaving behind only a pile of ash. The heat and pressure of this effect solidifies the ash into a hard, dark, crystal. This crystal is known as an eye of Sulfuras and is used by Ragnaros' followers in ancient rituals or to craft special weapons such as sulfuron hammers.
Note: This information, which may not be found in other sources, was taken from the More Magic and Mayhem RPG book.