Don't Underestimate

"Master… you've advanced?!" Heileen was dumbstruck as she sensed Xu An's body had undergone a complete change! His qi became more refined and his dantian slightly increased in size. That was not all, his body and soul had been tempered.

This results in him having a great number of impurities pushed out of his body, skin further toughened and tougher than steel, recovery rate increased a bit and his skin was whiter than before. 

By tempering and refining his soul with qi. His soul underwent a certain change and could now produce soul energy. Soul energy was stronger compared to qi and could increase his fighting prowess many times over. However, Xu An could not use it yet. The amount of soul energy his soul produced was little. When it reached the required amount, that was when he could use it.

That aside, Heileen had no words to utter and her movements stopped, which was a big blunder when you were being chased by a Heavenly Tribulation.