Perhaps because the Spirit Refining Art was a game reward, much like the One-Cubic-Meter Mobile Warehouse, Yan Ao didn't need any arduous training; he grasped it after a brief moment of practice.
"First, concentrate... and then—"
Gently closing his eyes, Yan Ao channeled the power of the sigil according to the method in his mind. Within a brief moment, he began to feel a pulsation radiating from his palm, and the source of that pulsation was none other than the Vajra Sigil.
Chapter 290