Xukong was a little shocked upon seeing the faces of Lin Mu's parents appearing on the dark figure's face.
"Why did Lin Mu never speak to me about this?" Xukong questioned himself.
'Has he been suppressing this in his mind all long, such that it has now turned into his Heart Demon?' Xukong thought to himself.
Indeed, the figure that was alternating between the two faces was none other than a Heart Demon. A Heart Demon is the product of the cultivator's emotions, memories, and guilt. They combine together and give birth to an entity that eventually becomes a Heart Demon.
A Heart Demon can gravely harm a cultivator if they don't deal with it or suppress it. Every cultivator that exists will one day develop a Heart Demon, the only difference is when. Even the most staunch, just, righteous, and willful of cultivators develop Heart Demons when they undergo their tribulations, not to say about the other common or unorthodox cultivators.