The level of Mystic Flames and Mystic Moon True Fire is vastly different; originally, Mystic Flames cannot possibly devour Mystic Moon True Fire.
To make an analogy, if Mystic Moon True Fire were like a hundred-foot divine dragon, then Mystic Flames would only be like a small snake as long as an arm.
Under normal circumstances, how could a small snake feast on a divine dragon?
Yet now, a massive hand is forcefully pressing this proud divine dragon into the ground, rendering it utterly incapable of resisting!
Taking advantage of this opportunity, this small snake can bite off a sliver of blood and flesh from the divine dragon!
Of course, if it were only that, the small snake still wouldn't be able to swallow the divine dragon whole!
Because the divine dragon's body is a million times larger than the small snake!
At this rate of devouring, it might take a thousand years to finish consuming the divine dragon!
