Metallurgy 2: Mystcraft Addon is an addon for for Mystcraft and Metallurgy 2. It allows Mystcraft access to Runes that allow certain ore types to be spawned only when that rune is crafted in a book. It has no effect if the default dimension spawning options in the Metallurgy 2 config are left unaltered (i.e. 0 & 2-10000 must be changed to 0, which would mean that ores only spawn normally in the Overworld).