Solution.

Valerian stopped after moving all over the place for a few minutes. He looked at Gladis with his glowing eyes without any fluctuation. The black dragon asked, "How did you do it?" 

His voice was hoarse than earlier, it was evident that Valerian's attack had done him a lot of harm, and he was enduring pain. Finally, the young man took a deep breath and said, "While you were focused on my movement, I attacked with this." 

He raised his left hand, revealing an azure-colored dagger. This dagger was made with materials that allowed Valerian to conduct wind attribute mana through the dagger to increase its sharpness. His strategy was to divert the attention of the enemy first. Then, attack him with the knife to disable him. 

Gladis shook his head and asked, "Your first attack? It was not this dagger." 

Valerian nodded and said, "Your scales are almost impenetrable. I could only use my wooden sword. Other metals do not affect dragons."