The older Yao Yao and Yu Jianjia shared the same bloodline, so she was the most suitable candidate to be the "medicinal catalyst."
Therefore, Song Mingzhao had gathered all kinds of expensive and rare medicinal herbs and poisons in the world, raising the older Yao Yao into a "medicinal catalyst" for Yu Jianjia to extract blood.
Every time the older Yao Yao was pricked with a needle to draw blood, a silver needle would be inserted into her chest.
This silver needle would make the older Yao Yao's heart feel like it was being stabbed by a knife. She would be in so much pain that she would rather die. Just like Song Mingzhao, her entire body would convulse.
When it was extremely painful, Yao Yao would even vomit blood. A maidservant held a jade bowl and specially for her blood.
This was the "heart blood" that Yu Jianjia needed.
After that, the silver needle was removed. They would not waste the blood that seeped out of her chest!