This Magic Crystal might be a high quality demon core that was refined for hundreds of years, used to safeguard the Demon King Statue. Although Yue Yang was surrounded by three Great Demon Kings and two Lich Kings at that time, he didn’t forget to greedily steal the Magic Crystal and brought it back home.
With the power from the huge Magic Crystal, the Demon Dragon’s Crystal finally managed to receive enough power up.
When the Hui Jin Magic Blade level up to Platinum Rank, Yue Yang carefully used his Nirvana Flame to purify the Flame Lord’s Blazing Core again. In the end, the evil awareness inside the Flame Lord’s Blazing Core had almost been destroyed completely, but because Yue Yang tried to control the evil awareness, half of it was preserved. The Flame Lord’s Blazing Core was almost destroyed, but it had levelled up to become “Flame Lord’s True Flame Core”, which had the ability to produce flames like the Nirvana Flame. The Hui Jin Magic Blade was now even more powerful than the Dragon Slaying Dagger which had absorbed a huge amount of darkness energy and Demon King’s evil intention.