The systems and other details involving a mage who manifests protective elements such as iron skin or stone-fist punches can be found in the Martial Arts section under Elemental

A legendary – and typically vulgar – feat of martial mastery allows a practitioner to channel elemental power into protective armor: searing flesh, buffeting winds, stony, wood or metallic skin, or other similar manifestations of power.

Story-wise, the martial artist focuses her practice through a certain type of elemental affinity that becomes, by extension, an integral part of her identity. This demands a fair amount of disciplined dedication; few martial artists master more than one form of element, and “casual” ones (brawlers and merely physical fighters) cannot use such elemental gifts at all.

System

-wise, the mechanics have already been covered above