Jagged Shard

Since crystals fracture along their planes of cleavage they naturally become sharper when broken.

The jagged shard is a weapon crafted from amethyst which is functionally similar to a sword but deals more damage the less durability it has. Damage increases exponentially with wear, so at full durability it is equal to a wood sword, at half durability it is equal to a stone sword, at a quarter iron, at an eighth diamond, and in the final few hits even more powerful than a diamond sword. The weapon's enchantability also increases as durability decreases, but once enchanted it cannot be repaired above the level it has been enchanted to. In the weapon's final hit when it breaks it deals a special shatter attack, which is much more powerful than a normal hit and in which the enchantments on the weapon are converted to damage, the more enchanted it was, the more damage the shatter attack deals when it breaks.