He had once seen this kind of spirit pill in the Treasured Pill Scripture. However, due to a shortage of certain spirit medicine, the Holy Church of Light did not have this spirit pill. He would usually consume animals to restore his blood essence.
For instance, Lu Zhen required a large amount of blood essence to regenerate her arm. Unfortunately, there was no such pill as the Strengthening Pill, so she had to rely on consuming more animals.
Still, by doing so, her blood essence could only be replenished at a limited speed, which was about ten days.
Besides, the restoration of blood essence also determined the condition of recovery. Just like regenerating an arm, if Lu Zhen had a rich supply of blood essence, her new arm would be strong. If her supply of blood essence was lacking, her regenerated arm would look like that of a baby's and it would take some time for it to become robust.