For quite a while I’ve been pretty confused by the term ‘cold iron’ that keeps cropping up in the old AD&D Monster Manual. Unless there is an explanation squirreled away somewhere in the DMG, ‘cold iron’ is left unexplained. (The demon entry mentions ‘iron weapons’ — nothing about them being “cold iron” — oversight or intentional distinction?)
I assumed from the beginning that it must mean something other than ‘regular off-the shelf weapons,’ for example, or else why not just say ‘normal weapons’ or ‘metal weapons,’ right? So my best guess was always that ‘cold iron’ must mean an archaic, non-steel iron, with some impurities but not much carbon. This would make them softer and more prone to bending and blunting than steel weapons, but a cold iron mace-head would be pretty much as good as a steel mace-head; it would be the bladed weapons that would really suffer from being made of regular iron.
For a while I tried to imagine ‘cold iron’ as some sort of iron that was worked without heating it, but I don’t think that is even possible with iron. Maybe you can cold forge copper or bronze. It couldn’t be cast iron either, which is usually alloyed to lower the melting point — so colder but less pure. Still I picture iron weapons as looking black or grey like cast iron.
Anyway my point is that I recently picked up a battered but usable copy of Lords of darkness, an AD&D supplement that has “Forgotten realms” and “introduced by Ed Greenwood” on it, but which is fairly generic and could be used in any setting. The book has a short explanation of various materials and tactics for fighting the undead, and a short passage on ‘cold iron’ which explains that this is special iron with no impurities. There is a brief mention of the tendency of cold iron weapons to break easily, and while there are no mechanics offered for that, I’d say they might break on a natural one on an attack roll (I don’t otherwise use ‘fumbles’ in my current game).
(Checking Wikipedia for this post, I see it suggested that “cold iron” is just an archaism for “iron” since iron is usually cold to the touch. Nothing special about it at all, just plain old iron. I’d like to try out a setting where elves are susceptible to iron weapons too, since in folklore the fairy folk are fearful of it and several of Poul Anderson’s fantasy stories and novels use this idea a lot. I’m not sure if that would work well in my current game but I’ve had events shake up how magic works before so there may be a way to make it happen.)
Anyway if you should stumble across this supplement, it is worth looking over. The scenarios look all right (two are by Paul Jaquays!), although there is certain amount of railroading in one I read. There are also nice discussions of undead, including a number of alternatives to energy drain and the ghost’s 10 year aging effect. The proposed solutions to these perennial “problems” shed some light on the state of the game when it was published.
Some of the interesting tidbits are suggestions for the effects of various anti-undead folk remedies like knocking on wood (useless), mirrors (only good vs. vampires), and salt (useful against a lot of the undead). There is even a chart listing how various means affect all the undead from the Monster Manual, Monster Manual II, and Fiend Folio! The whole thing is pretty cool as a source book on using the undead.