It was the rainy season. Wu Xuan had been diligently practicing with the Black Iron Sword day and night for several days. That evening, torrential rain poured outside the cave. Dugu Qiubai emerged from meditation, glanced at the downpour beyond the entrance, then turned to Wu Xuan. "Kid, take the Black Iron Sword and come with me!"
With that, he headed straight out of the cave. Wu Xuan knew Dugu Qiubai was taking him to practice heavy sword techniques amid the mountain floods. Yet he was shocked to discover that the drifting rain could not wet Dugu Qiubai's clothes at all. The rainwater slid away on its own when it came within an inch of Dugu Qiubai, flowing down into the ground.
After following Dugu Qiubai for several miles, Wu Xuan faintly heard an unceasing roar, clearly the sound of massive rushing water. Before long, they arrived before the waterfall they had visited before. But now, with the rain pouring down, the force of the water was incomparable to what it had been then.
At the edge of the stream where the mountain floodwaters gathered beneath the waterfall, Dugu Qiubai tilted his head and said to Wu Xuan, "Get down there. Practice your swordsmanship in the flood!"
The current was raging at the moment. Even though Wu Xuan had practiced martial arts in water before, he could not help feeling apprehensive.
After calming his uneasy heart, Wu Xuan gripped the Black Iron Sword and stepped into the floodwaters one step at a time. The current was fierce when he first entered. Unsteady on his feet, he was swept back several steps by the rushing water. He immediately circulated his qi and used the Thousand-Pound Drop technique to steady himself.
Drawing on his past experience training in water, together with the