Precious items in gold (usually) settings that can enhance items with charm slots. Smaller than matrices
Fire charms are made of fire gems and provide fire defense in armor and fire damage in weapons. Fire arrows could start fires. A fire pick might melt snow.
Acid charms are made with acid gems add "caustic" effects. Caustic pick is faster but destroys material.
Diamond charms make tools and weapons stronger, but the diamond wears out after a while.
Crystal charms can be turned into blood charms if they are placed in weapons and the weapons are used x times.
Blood charms provide vampiric healing or can be broken to receive gold and a blood crystal .
Light charms are made with light crystals and allow a tool, weapon, or armor piece to emit light.
Obsidian charms are made with obsidian and adamantine and have lava effects. In armor it protects from lava. In helmets it protects from smoke. In boots it allows lava walking. In buckets or barrels , it lets them hold lava