Some argue that it was the rise of the Iron Age that caused the Sundering and so it has become the Sundering incarnate, as it were. Its presence makes the fae uncomfortable and wounds caused by weapons made of the stuff leaves horrible, smoking wounds that destroy Glamour and can bring about death to the fae soul. So distasteful is it, that the kithain can sense when it is near.
Like many things in the world, Cold Iron is a bit of a paradox. Steel contains more of the element in it than cold iron itself does. Most of what we think of as iron today is actually steel or cast iron (cold iron melted and poured in a mold). Cold Iron is what we know as wrought iron. It is not a thing, per se, but more of a process... a very low-tech process. It must be produced from iron ore over a charcoal fire and the resulting lumps must be hammered into useful shapes.
Cold Iron weapons are heavier, softer, more brittle than steel and loose an edge quickly. Such a weapon larger than a dagger is unwieldy with a +1 or +2 difficulty modifier. Botches almost always cause breakage. So such weapons tend to be small: axe heads, daggers, arrowheads, darts, bolts, caltrops and shuriken. The making of such weapons is illegal in most Kingdoms, though many a noble has a secret one just in case. Mortal blacksmiths who can work with it are highly prized and finding the ore is actually fairly easy. Alabama, Utah, Texas, California, Pennsylvania, and New York all have mines. It is rumored that some mages can produce cold iron weapons with properties of steel. It is also believed that a weapon quenched in changeling blood is harder to sense.
House Dougal Edit
For more information about Cold Iron, see the article House Dougal.