Originally Posted by BRC
Am I the only one who thinks that would actually be very interesting, not just as a vague concept, but as an actual RULE in the setting. If the Forces of good create a Holy Sword, they must also create an Unholy Sword with the exact same properties, same goes for the forces of Evil creating an Unholy Sword. If you destroy an item like this, it's "Twin" is also destroyed. Therefore, the forces of Evil keep building elaborate vaults in which to hide "Good" magic items (So they can use the Evil ones on the front lines), while the forces of Good do the same thing with the Evil items that they keep building while attempting to equip their own forces. If you manage to raid these vaults you get a bucketload of magic items that you can wield yourself, or destroy to deprive the enemy of the use of their twins.
Neutral, unaligned items can be created, but they can be used by either side, and can therefore be easily looted in battle.
Of course, this requires that the setting be based around some big cosmic struggle between "Good" and "Evil".
Unless each side refers to itself as the "Good" side, wielding "Holy" Weapons against their "Evil" foes, with each side excusing their crimes as "The Neccessities of War", while pointing to "The debased and vile nature of our foe" every time their enemy commits some atrocity.
Interesting idea. The Saga of Recluce series by L. E. Modesitt uses something along these lines. The main struggle in the setting is between Order and Chaos, and mages are either "black" order mages (can use order to strengthen things, harden air into barriers, and such), "white" chaos mages (can use chaos to degrade things, shoot fire, and such), or "gray" druids (can use both order and chaos), and all of them have some shared tricks like bending light to turn invisible, knowing when people lie, and similar, though their methods of doing so depend on whether they use order or chaos.
for a full summary, but basically the most ancient empire in the world ran on chaos (essentially using it as a form of fusion power to run ships and power weapons), but eventually fell due to their technology failing and Order became ascendant. Order and Chaos traded ascendancy for a while, and we find out partway through the series that the Balance works to keep things balanced, so the more chaos there is in the world the more order there is as well and every "chaos focus" (extremely powerful chaos mage) is balanced by the rise of an "order focus."
The order forces develop ships running on chaos-engines contained by order-hardened iron, dramatically increasing the amount of both order and chaos in the world, and in fact they are deliberately increasing the amount of chaos in the world available to their enemies in the hopes of strengthening themselves, because most of the order is concentrated in one group while the chaos mages are widely dispersed. The cycle keeps escalating until it gets so bad that the druids have to pretty much wipe out most of the world's order and chaos to prevent Bad Things from happening.
Combining that with your suggesting, to make Law and Chaos conserved quantities as much as Good and Evil, would actually explain a lot. The Blood War, why magic items are stored in dungeons, the way villains seem to keep coming back unabated, why BoED and BoVD work the way they do, and more. I'll probably use something along those lines from now on.