Flawless Phlogiston Development Materials A premium material used for Weapon Ascension and Skill Upgrade for Pistols Resonators.

A crystal shaped like a raging flame, known for its impeccable purity. As a result, some Resonators don't want to use these crystals solely for enhancement, instead opting to entrust professional craftsmen to process them into unique accessories.
Sources
Forgery Challenge: Abyss of Confession
Synthesis - Purification
Synthesis - Conversion
Forgery Challenge: Marigold Woods