(Heartfelt thanks to 'kkkkkk x', 'Yan Ai Ai', 'Wufeng Haotian', 'Little Xi Fat Goat', and 'Half-Sword Qingcheng' for their tips!)
The innate source of magical power possessed by every magus.
This was a Magic Circuit.
They were pseudo-nerves within a magus's body, as well as the qualification that made one a magus. They could convert a magus's life force into magical energy, connected closely to the Magic Foundation, and enabled magi to perform artificial miracles—magecraft.
In other words, Magic Circuits were the most fundamental proof of a magus.
Only by possessing Magic Circuits could one possess magical energy, perform magecraft, and become a magus.
Yet Magic Circuits were determined at birth.
Whether they existed at all, their quantity, or their quality, none of it could be increased through external factors.
Because they were exceedingly rare to begin with.
Thus, in order to pass down their family magecraft and let later generations inherit their research, hoping that one day they might reach the Root, magi usually accumulated their bloodlines over several generations so their descendants would be born with bodies more suited to magecraft.
If people who were already magi joined together, their descendants would have a high chance of possessing Magic Circuits. Some particularly outstanding children could even possess excellent Magic Circuits, laying a tremendous foundation for becoming exceptional magi.
Therefore, in the world of magecraft, there were families that went so far in order to produce descendants with outstanding Magic Circuits that it was practically like selective breeding, all for the sake of increasing the number of Magic Circuits their children were born with.
Of course, there were also exceptional cases where Magic Circuits mutated into existence within ordinary families, but those were exceptions among exceptions.
Naturally, since there were examples of mage families producing descendants who became more