Mithril is a fictional
metal originating in J.
R.
R. Tolkien's Lord of the Rings series.
It is called 'true
silver' by the Dwarves and is an incredibly durable and lightweight substance only found in the mines of Khazad-dûm.
In the grand tradition of stealing ideas from Tolkien, countless fantasy authors and game designers have introduced this material into their works.
Often misspelled as mythril, mithral, or mythral and probably mutated into mistral, etc...