How to complete Four Fierce Axes in Phantom Blade Zero

The Four Fierce Axes quest in Phantom Blade Zero requires gathering seven "Four Axes" case files, starting with one found in Broken Puppet Valley and continuing across Weeping Creek Valley and other regions. The sixth file comes from the lieutenant in the Festering Secret quest, while the seventh only becomes accessible after reaching the Village of Lu and starting Leave None Alive. Delivering all the evidence to the Child of Insight in Pangzhen rewards the Blood Oath Dagger, which Soul Tempers the Dread Axe once the ability is unlocked with Myst.