A magma forge is a metalsmith's forge which uses magma instead of other forms of fuel, freeing up all of your charcoal and coke for the production of pig iron and steel. This convenience comes at a cost, however - the magma forge must be built along the magma flow (magma-filled channels will not work), exposing your metalsmiths to any dangerous creatures that may decide to emerge from the magma.
 Metal clothing
Once you discover adamantine, it becomes possible to make adamantine clothing, but only at a magma forge. All the clothing items that can be made at the clothes maker's shop, as well as backpacks and quivers, can be forged from adamantine cloth.