In simple terms, spirit marrow was the essence of a spirit vein. Although spirit marrow truly existed, not every spirit vein contained it.
The Spirit Realm had a saying: "From ten thousand veins comes one marrow."
Though that was how the saying went, when it came to spirit marrow, ten thousand spirit veins absolutely could not give birth to even one vein containing it. Even among a hundred thousand spirit veins, it was hard to say whether one would truly contain spirit marrow.
Of course, perhaps spirit marrow was everywhere in the Miro Realm, but in realms equivalent to the Spirit Realm, it was absolutely difficult to say that spirit marrow existed.
Although spirit marrow could not be consumed, it could increase the density of spiritual energy in an area.
Moreover, the purity of the spiritual energy transformed from spirit marrow was far beyond that of spiritual energy from other spirit veins. If one secluded oneself in such spiritual energy, the speed of absorbing and refining it would be difficult to match even in a chamber at the eye of a spirit spring.
At that moment, before Qin Fengming was a slender black thread as fine as a strand of hair, winding through a mark as thick as a baby's finger. The mark was several miles long and lay precisely in the middle of the entire underground cavern.
Although the thread was slender, it was wrapped in a cluster of incredibly luminous five-colored fluorescence.
The fluorescence contained indescribably powerful spiritual energy. When divine sense touched it, it was directly bounced away by the fluorescence. It was as if the fluorescence had become solid, hard as iron.
Qin Fengming had never seen spirit marrow before, but judging from the condition and form described in the ancient texts, he immediately determined that