The [Rainbow Forge Manual].
Written by the former Kaijin Lord known as the Rainbowsmith, this manual detailed the forge master's personal insights and techniques he had developed when it came to three important aspects of his work.
The first was a detailed chapter on how to best bring out the raw power in the various materials he had handled over the years.
Not all metals melted at the same temperatures, and not all materials reacted the same way when exposed to certain stimuli. Hell, some materials even reacted in strange an unpredictable ways when brought together.
This type of insight can usually only be taught through experience, but the Rainbowsmith's account was detailed enough to make it possible for even a novice to pick up with great ease.
This alone made the manual valuable, but not quite priceless.
