Now, the only thing that could truly enhance his physical quality was the Asyncritus Spirit Root, but this thing was like growth; you couldn't just force it, or it would easily be ruined.
And while the Marked Druid did increase his physical quality, that fixed value was nothing. Gu Shanhai needed percentile increases, like how the six natural marks of the first layer gave him an additional 50% attribute increase for his six attributes—now that was true power.
But to forge iron, one must be strong oneself: even with an additional 50%, 1 point of attribute would only be 1.5 points.
Attributes, however, shouldn't be taken too literally. Gu Shanhai didn't have any numerical data and had to rely solely on his intuition instead of complete quantification.
So, he needed a way to enhance his attributes autonomously, like Mana, and not just through growth.