Mystic Power, it's a new kind of source energy that works on the same principle as inner energy like Qi. But unlike Qi, mystic power is pretty violent that caused an average human body to reject or resist it subconsciously if they couldn't adapt to it. It was for that reason it was dubbed as violent energy or in some other case, wicked. But if one was able to adapt to it, their body will slowly grow stronger by its influence. Of course that doesn't mean the energy becomes docile enough for them to fully control it as pleased. If they even make a small mistake in channeling the mystic power within their body, they will have to suffer the consequence of it.