Mythril Ore is the fifth hardest ore in the game. This mineral can only be mined by a Cobalt Drill/Pickaxe or higher. It is found rarely around the world, mostly in the rock layer, or below -600 feet.
Mythril Ore can be spawned into your world by breaking a Demon Altar with a Pwnhammer or Drax. This also applies to other types of ores, such as Cobalt and Adamantite. Upon breaking a second Demon Altar after first loading the world, the Mythril Ore will be placed in your world and the text "Your world has been blessed with Mythril!" will appear. Mythril Ore, together with Cobalt Ore and Adamantite Ore cannot be broken with Explosives.
Mythril is required to craft Mythril gear. It must be smelted into bars at a furnace, however.
Mythril is a reference to J.R.R. Tolkien's Lord of the Rings. Mythril or "mithril" in the books resembled silver, was stronger than steel, and was lighter than both of them.
Mythril appears in other games, such as RuneScape, Guild Wars 2, Diablo II, World of Warcraft, Shining Force II, Chrono Cross, Final Fantasy, Zenonia 3, Xenoblade Chronicles, NetHack, Golden Sun, and The Elder Scrolls IV: Oblivion
Mythril has been known to also be spelled and said as mith, mithral, and mithril.