The Nine Netherworld Yellow Springs Diagram was one of the Holy Demon Sect's sect-protecting treasures.
It was said that, in order to refine this treasure, the Holy Demon Sect's five great Demon Patriarchs had jointly ventured deep into the Nine Netherworld and subdued this Nine Netherworld Yellow Springs.
All thirteen Demon Patriarchs of the Holy Demon Sect had been giants at the peak of the Heavenly Immortal Realm.
The five great Demon Patriarchs were five peak Heavenly Immortal Realm existences.
The Nine Netherworld Yellow Springs Diagram had played a vital role in allowing the Ten Thousand Gu Demon Patriarch to escape the pursuit of seven Heavenly Immortals.
According to the records within the Cosmos Mirror, when the Ten Thousand Gu Demon Patriarch fled back then, he had also sealed six of the Holy Demon Sect's spirit veins inside this diagram.
Each of these six spirit veins stretched for more than a thousand miles.
However, when he later refined the Immortal-Eating Gu, he not only used himself as nourishment but also sealed one spirit vein within the Gu Immortal Jar.
That was precisely why the Immortal-Eating Gu's Source Gu had survived for so long.
It had devoured that spirit vein and undergone two transformations.
Lin Fei had not seen the spirit vein inside the Gu Immortal Jar because the golden Immortal-Eating Gu had already devoured it completely.
"The five spirit veins within the Nine Netherworld Yellow Springs Diagram, each over a thousand miles long, are exactly what I need."
"Besides those five spirit veins, there are also over a dozen smaller ones. When the Holy Demon Sect was at its height, it is truly hard to imagine just how glorious it must have been!"
"This diagram is of great importance and cannot be exposed lightly. If the Heavenly Dao Alliance learns