In Chen Fei's spiritual perception, as the Heart Refinement Formation operated, wisps of black mist continuously overflowed from the mysterious source of the heart.
Whether it was the black mist or the source itself, they were invisible to the naked eye, only discernible by the spirit. The black mist twisted and drifted out of the Heart Refinement Formation, and after a moment, a pure source undulated within the array.
A faint smile appeared on Chen Fei's face, but it gradually faded as he observed the consumption of the Strange Heart Stone.
This was the real world, and even the most peak Heart Refinement Formation couldn't extract energy from the Strange Heart Realm. Naturally, to activate the Heart Refinement Formation, he could only use Strange Heart Stones.
