With justice as god and evil as the devil, the combination of justice and evil was the fiend.
The so-called power of the inner demon was akin to the center of justice and evil, the center of darkness and light, the point of meeting between heaven and earth.
It was strange and unpredictable—something that consumed both light and dark. It was essentially a crazed spirit that showed contempt to all rules in the world.
Take Xia Fei for example; it was inaccurate to call him a good person, as there were countless who had died by Xia Fei's hands, which were coated in blood. To call him evil would be inaccurate as well; seeing the meticulous concern and care he showed toward Avril as well as how deeply in love he was, most people in the world would consider him to be a righteous protector whom other gentlemen would be ashamed of.
Xia Fei had even said so himself; he only cared about those whom he wanted to care about, while the others were just decorations.