Perfect resonance.
This was the fundamental essence of the Forging Technique.
The Forging Technique could only truly take effect when a perfect resonance was achieved between one's Spirit, body, Energy, and life essence. It used the combined power of these four elements to constantly vibrate, weeding out the subtle "impurities" that failed to resonate in perfect harmony. This, in turn, purified and refined one's life essence.
The requirements for this resonance were extremely high. Even the slightest deviation could prevent the Forging Technique from working. Instead of eliminating the "impurities" from one's life essence, it would cause immense damage to it.
Even he couldn't immediately find this perfect resonant frequency. Or rather, he knew it would be incredibly difficult to master such an ultimate balance on his own. Otherwise, breaking through the Transformation Boundary wouldn't be considered such an insurmountable barrier.
