Armor made from volcanic glass is sharp and dangerous but fragile. While wearing obsidian armor, your natural weapon attacks or unarmed strikes deal an additional 1d4 slashing damage. However, the armor shatters if you take more than 20 damage from a single attack, and becomes permanently destroyed. Obsidian armor costs the base price of the armor plus 100 gp. Only light or medium armor can be made from obsidian.