Miner Artisan

The Miner If you’re lucky enough to place your stronghold near a source of metal—which, it turns out, you did if you attract a miner—such as a natural cave or a valley dug by an ancient river, you can extract metal near the surface. An experienced miner can survey the terrain in a moment and tell what kind of rock you’re on, what kind of ore can be found underneath, and how long it will take and costly it will be to extract. They bring with them their own experienced crew and often their families. As many as thirty men and women could be working your mine by the end of the first season. 
THE MINE: The ore extracted from your mine is valuable, and you can sell what you don’t use in improving your stronghold and the weapons and armor of your units. A mine produces 500 gp per season. In addition, a mine improves the equipment of some number of your units by one level—a light unit becomes medium, medium becomes heavy, etc. This bonus can be applied to one unit per mine level, as it includes the time and cost of maintaining their improved equipment.