By now most of the common people of Chang'an had either passed out from the qi pressure or were hallucinating and frothing from the mouth. The practioners and cultivators who were once hailed as the mighty among the gentle folk of the city were cowering in hidey holes. They knew what was at stake here, if the Heavenly Emperor lost today's conflict, the heyday of Great Tang was over. The Empire would be torn down and a Heavenly Demon would sit on the throne of the World. Each of them cursed Cao Li for ruining thus the hegemony of Tang. For even if the Emperor won today, news of this battle would travel to the furthest parts of the Empire and all would know that Great Tang was not as strong as they once pretended to be. 

Cao Li in turn bit his lip until blood dribbled down his chin, as he stared at this awe inspiring battle from underneath a horse cart. He could still not believe that his junior was capable of such greatness. For Zang to be acknowledged as the Heavenly Demon was a great humiliation to Cao Li who knew that he would never reach this level of power.  

Not unless things changed, drastically. 

In the azure sky, the Emperor riding a golden blade made of lightning clashed with Zang Yuang himself astride a crimson dragon made of lightning. The two god like forces danced around each other again and again, their qi crashing against each other with the sound of brass gongs. Songs would be written of this day for many centuries to come, but the two practioners were unaware of this. Through their unending attacks one slowly started gaining the upper hand.  It was the Emperor Tai'zong, with his monstrous techniques, who landed the first blow. 

"Blood Splitting Golden Palm" 

He shouted as his palm found a way through Zang's defence and landed square on his chest, the golden qi of the Emperor rushed into Zang's middle dantian, attacking the walls of his Blood Soul Palace. Zang spat out blood in a misty spray and felt his cultivation crumble. Was this the end for him then? Zang's vision was swimming, he was seeing two Emperors looming in front of him, within seconds he was going to black out and then bleed to death unless he did something. 

No

The torrential qi of Heaven and Earth was still raging into his body, if he could only keep his focus for one moment and take in a single breath then... 

"Not so fast, eat this! Ten Thousand Golden Fists of Heaven."

The Emperor was on him like a cobra ready to devour his prey, unleashing a barrage of fist attacks overflowing by his pure golden qi. Zang laughed, so his plans were all for naught after all. Cultivation levels were not the end after all, today it was abundantly clear to Zang that one could not replace experience in battle and techniques with the brute force of a higher cultivation level. Still if he was going to die, he might as well take the Emperor with him. A long time ago his teacher had told him about the forbidden qi draining techniques, although his sifu had never taught him those forbidden skills, for a genius like Zang it was child’s play figuring them out. Theoretically he understood how they functioned, practically of course this was going to be his first attempt at trying them out.

The theory behind the technique was simple, you exhale, expelling all your stored qi in one breath creating a void within your middle dantian and forcing the qi out of your opponent's channels and into your body and your three dantians. Unfortunately in the heat of the battle Zang did not realize that this theory only applied to a healthy body with three functioning dantians. Zang's upper dantian was crippled and open, his lower dantian was sealed and his middle dantian was a blood soul palace. His fading eyesight saw the punch headed towards his face and with a herculean effort Zang managed to catch the Emperor's wrist.

Without waiting he exhaled and forcefully expelled all his qi. The Emperor was not expecting this and stared at Zang slack jawed.

There was a moment of dreadful silence. The raging torrent of the qi of heaven and earth slowed down to a mere trickle and Zang experienced blissful silence in his head for the first time since he had opened his crown dantian. In the next moment however his crumbling soul palace began to twist and deform. Zang's eyes grew wide with surprise. 

The void, the void was forming. Only this was a void unlike any other....this was a Black Hole.