The Fire Phoenix was a double mutated transcendent monster. It had encountered human before so it understood human language. It got even more furious when Lin Huang challenged it! Although it had no idea what was the black piece of cloth that he was using to defend its first attack, it was surprised that he managed to defend himself. However, that attack was not its most powerful attack. It did not think that the black shield could protect Lin Huang during its following attack.
Meanwhile, Lin Huang had never wanted to use Dark Shield to fight until the end. His objective of entering this dimensional ruin was to strengthen himself by going through the training. Although the Fire Phoenix was powerful, it was not as powerful to the extent that he would want to run away. On the contrary, it benefited him when the Fire Phoenix pressured and gave him the confidence that he would survive this battle. That was the reason why he challenged the Fire Phoenix.