It was too harsh.
After being done absorbing a few Gold Cores, Wu Qi inspected the condition inside his body using his divine sense. What he found made him lament. Indeed, the Scroll of Stealing was a profound and fantastic cultivation technique, but at the same time, it was extremely harsh on those who cultivated it. Even after absorbing so many Gold Cores, it only made all ten False Cores of his became slightly solidified. It was only after he absorbed these Gold Cores that Wu Qi realized that Scroll of Stealing would only extract one single thread of purest core energy from them, which was the Innate Nectar produced from the merging of Gold Core and the cultivator's soul. Only the Innate Nectar was merged with his False Cores, while all the other energies of the Gold Core, 99% of them, were discarded.