Obsidian. A black, glasslike rock formed from volcanic activity, that can be polished to be glossy and reflective. It has garnered a reputation for various mystical properties and superstitions surrounding it, the most prominent of which being its association with demons. Obsidian was used in the stone age to make many tools such as arrowheads, and even today an obsidian tool can qualify as an AbsurdlySharpBlade.