Yaaay this sounds fun.
A dark red metal that, no matter how it is worked, always seems to shine like wet blood due to its strange structure. It seems to have some power to reinforce order in other materials. In most respects, it functions as cold iron. However, it develops additional qualities depending on how it is used.
For starters, red ferum doesn't rust or corrode and is immune to any such effect. When a red ferum weapon or armor is used by a creature of lawful alignment, it deals an extra 1 point of damage to chaotic creatures when made into a weapon or provides DR 1/chaotic when made into armor. When used in chains or other restraints, the break DC increases by 10, the hardness increases by 5, and the Escape Artist DC increases by 5. Only items primarily made of metal can be made of red ferum, things such as spears cannot be made of red ferum.