True Gap

Nothing was left; the whole body was sucked in by the Devouring Martial Spirit. (Martial Soul=Martial Spirit)

But it didn't look much evil since Fei wasn't the eating flesh; instead, his Devouring Martial Spirit was eating it. It completely crushed the demon boss body, slowly turning it into dust, and refining dust to produce energy. All of this was happening inside the Devouring Martial Spirit.

His eyes were closed, concentrating on his Martial Spirit, and energy released by his Martial spirit.

When this energy was produced, it silently flew into Fei's blood. It began to integrate with Dream Bloodline that is hidden inside his body. But suddenly Fei stopped it, and then Fei began to control it, taking it slowly to his eyes.