The earth veins that were merged into the body were a little different from the spiritual veins in external pills. All external pills were made up of gold or stone, and even if they were broken or spoiled, it didn't matter. The goal was for strength, and naturally the purer it was the better.
When merging the earth veins into the nine Bodily Chakra Meridians, one needed to care about the five elements, not letting the five elements of the human body become imbalanced. One could only choose to focus on one or two elements based on their different cultivation methods.
Which was why, although the amount of spiritual veins in the world were endless, only a small number of them were suitable for Xiantian Masters.