Mythril (item)

Mythril is a valuable metal, second only to Adamantite, found in the Final Fantasy series. It can be crafted into many pieces of equipment, like swords, armor and gauntlets. The name seems to be derived from a metal called Mithril, appearing in J.R.R. Tolkien's fictional universe, featured in "The Hobbit" and "The Lord of the Rings".

Final Fantasy II
The party needs to find Mythril, which is guarded by an Adamantoise.

Final Fantasy VII
There is a Mythril Mine the party must pass through on the way to Junon. There is also a piece of Mythril that can be obtained from an old man, that can be traded for Aeris' best Limit Break.