The dragon heart quickly decreased in size as the sect mistress absorbed the blood within.When Kai Syaoran saw this, he confirmed his suspicion that Lui Yifei was a descendant of the Frenzied Dragon emperor. This was the only way she would be able to absorb the blood so fast without any signs of rejection.
For demonic beasts, their bloodlines were precious and for this reason, they go to great heights to protect their blood from other creatures, especially the human bloodline cultivators. The blood is embedded with remnant consciousness and for powerful creatures such as the dragon emperor, absorbing their blood requires their agreement. The only other method is for one to be powerful enough to suppress the remnant consciousness. Since the sect's mistress was nowhere near as powerful as the Frenzied Dragon emperor, then she had to have the recognition of the emperor. This recognition is in most cases only given to blood descendants.
