If the title of the next chapter is External Spirit Bones, Grandmaster actually mentioned spirit bones before, in that saying. "Rings many, bones many, power surges, rings few, bones few, run for your life". (I'm paraphrasing). Then he said, "I'll tell you about spirit bones later."
So the legs are probably spirit bones. And the reason that Zhao Wuji has never seen such a thing before could have to do with the fact that he's A) young (in comparison to many people of his rank) and B) unconnected to any sort of major power.
So the reason the next chapter is explicitly called "External Spirit Bones" is because most spirit bones are formed inside the body, when absorbing a particularly suitable (or tough) spirit. Probably.
So, the fun part is, what are spirit bones?
I have two theories: one is that they are relics left behind by spirit masters of ancient times, and no one knows how to make them anymore. They serve a purpose very similar to spirit tools, or serve in the creation of spirit tools. Tang San has just rediscovered how to do it, by withstanding a spirit ring that he shouldn't have been able to absorb
The other is that, when a spirit ring absorption process gets really difficult for the spirit master, or when the spirit ring is particularly suitable for that spirit master, he forms what is called a spirit bone, which does one of three things: aids in future cultivation, increases spirit power, right off the bat, or increases physical power/regeneration.
I don't know anything for sure, I'm just speculating.
So the legs are probably spirit bones. And the reason that Zhao Wuji has never seen such a thing before could have to do with the fact that he's A) young (in comparison to many people of his rank) and B) unconnected to any sort of major power.
So the reason the next chapter is explicitly called "External Spirit Bones" is because most spirit bones are formed inside the body, when absorbing a particularly suitable (or tough) spirit. Probably.
So, the fun part is, what are spirit bones?
I have two theories: one is that they are relics left behind by spirit masters of ancient times, and no one knows how to make them anymore. They serve a purpose very similar to spirit tools, or serve in the creation of spirit tools. Tang San has just rediscovered how to do it, by withstanding a spirit ring that he shouldn't have been able to absorb
The other is that, when a spirit ring absorption process gets really difficult for the spirit master, or when the spirit ring is particularly suitable for that spirit master, he forms what is called a spirit bone, which does one of three things: aids in future cultivation, increases spirit power, right off the bat, or increases physical power/regeneration.
I don't know anything for sure, I'm just speculating.