In addition to magic items created with spells, some substances have innate special properties. If you make a suit of armor or weapon out of more than one special material, you get the benefit of only the most prevalent material. However, you can build a double weapon with each head made of a different special material.
Each of the special materials described below has a definite game effect. Some creatures have damage reduction based on their creature type or core concept. Some are resistant to all but a special type of damage, such as that dealt by evil-aligned weapons or bludgeoning weapons. Others are vulnerable to weapons of a particular material. Characters may choose to carry several different types of weapons, depending upon the campaign and types of creatures they most commonly encounter.
This iron, mined deep underground, known for its effectiveness against fey creatures, is forged at a lower temperature to preserve its delicate properties.
Weapons made of cold iron cost twice as much to make as their normal counterparts. Also, any magical enhancements suggested cost an additional 2,000 gp. Items without metal parts cannot be made from cold iron. An arrow could be made of cold iron, but a standard quarterstaff could not. A double weapon that has only half of it made of cold iron increases its cost by a suggested 50%.
Cold iron has 30 hit points per inch of thickness and hardness 10.
Armorsmiths can work with the hides of dragons to produce armor or shields of masterwork quality. One dragon produces enough hide for a single suit of masterwork hide armor for a creature one size category smaller than the dragon. By selecting only choice scales and bits of hide, an armorsmith can produce one suit of masterwork banded mail for a creature two sizes smaller, one suit of masterwork half-plate for a creature three sizes smaller, or one masterwork breastplate or suit of full plate for a creature four sizes smaller. In each case, enough hide is available to produce a small or large masterwork shield in addition to the armor, provided that the dragon is Large or larger.
Because Dragonhide armor isn’t made of metal, druids can wear it without penalty. I suggest that Barbarians may be able to wear as well. Dragonhide armor costs double what masterwork armor of that type ordinarily costs, but it takes no longer to make than ordinary armor of that type.
Dragonhide has 10 hit points per inch of thickness and hardness 10.
Mithril is a very rare silvery, glistening metal that is lighter than iron but just as hard. When worked like steel, it becomes a wonderful material from which to create armor and is occasionally used for other items as well. I suggest that most mithril armors are one category lighter than normal for purposes of movement and other limitations. Meaning, Heavy armors are treated as Medium, and Medium armors are treated as Light, but Light armors are still treated as light regardless.
Spell failure chances for armors and shields made from mithril are decreased by 10%, maximum Dexterity bonus is increased by 2, and armor check penalties are lessened by 3 (to a minimum of 0). These, of course, may be modified as needed for use in your own campaign.
As noted previously, an item made from mithril weighs half as much as the same item made from other metals. In the case of weapons, this lighter weight does not change a weapon’s size category or the ease with which it can be wielded (whether it is light, one-handed, or two-handed). Items not primarily of metal are not meaningfully affected by being partially made of mithril. (A longsword can be a mithril weapon, while a scythe cannot be.) Weapons or armors fashioned from mithral are always masterwork items.
Mithral has 30 hit points per inch of thickness and hardness 15.