Mithral 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 armour and is occasionally used for other items as well. Most mithral armours are one category lighter than normal for purposes of movement and other limitations (for example, whether a barbarian can use her fast movement ability while wearing the armour or not). Heavy armours are treated as medium, and medium armours are treated as light, but light armours are still treated as light. Spell failure chances for armours and shields made from mithral are decreased by 10%, maximum Dexterity bonus is increased by 2, and armour check penalties are lessened by 3 (to a minimum of 0).
An item made from mithral 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 mithral. (A longsword can be a mithral weapon, while a scythe cannot be.)
Weapons or armours fashioned from mithral are always masterwork items as well; the masterwork cost is included in the prices given below.
Mithral has 30 hit points per inch of thickness and hardness 15.
| Type of Mithral Item | Item Cost Modifier |
|---|---|
| Shield | +1,000 gp |
| Light Armour | +1,000 gp |
| Medium Armour | +4,000 gp |
| Heavy Armour | +9,000 gp |
| Other Items | +500 gp/lb. |
Source: Dungeon Master’s Guide (Page 284)