Mithril Bar

Mithril Bars are smelted from Mithril Ore, and are heavily used in Blacksmithing, Engineering, and Jewelcrafting. The Mithril Order was named after the mineral.

Source
Mithril Bars can be created at a forge by miners with their smelting skill. It requires a mining skill of 175.

As an ingredient
Mithril Bar is used in the following recipes:

Alchemy

 * Transmute: Mithril to Truesilver

Engineering

 * Deepdive Helmet
 * Unstable Trigger
 * Mechanical Repair Kit
 * Mithril Blunderbuss
 * Mithril Casing
 * Mithril Tube
 * Mithril Heavy-Bore Rifle
 * Mithril Mechanical Dragonling
 * Snowmaster 9000

Jewelcrafting

 * Citrine Ring of Rapid Healing
 * Mithril Filigree

As a quest objective
Mithril Bar is needed for the following quests:
 * Smelt On, Smelt Off
 * The Great Silver Deceiver
 * The Art of the Imbue

In the RPG
Mithril is a 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; it is occasionally used for other items as well. Most mithril armors are lighter than other metals. 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 the weapon’s ease with which it can be wielded (whether it is light, one-handed or two-handed). Items not made primarily of metal are not meaningfully affected by being partially made of mithril.