All members of the demon race can draw magic power from the demon veins. This power isn't innate but is stored in the demon veins after the demon race members return to their roots.

Take, for example, the former four concubines' sacrifice or an elder like Kuisaile. When their time comes, they choose to return to the demon veins, returning to their roots.

Once absorbed by the demon veins, their cultivation level and strength are entirely stored within.

When the core of the demon veins transformed back into a mass of chaotic meat fungus, Qin Yi held it in his hand, clearly sensing the immense energy contained within.