Review Detail of B_V_Ashutosh_8 in Villain's Survival: I refuse to be the Mc's stepping stone

I don't want to spoiler but for your question I can assure you favian will have complete control over himself though , there is much space for the devil to fight for his soul. Ever watched JJK, in the shubuya arc, one of the curses try to tell the main anatgonist that is in a certain sense similar to our devil, to force his host to sign a contract in favor of him by using his friends as hostage. Such thing can be done even in this novel, Favian know this too and he knows that using his power fully is too dangerous and must be used as last ditch effort knowing also that if he is discovered by the kingdom he will be basically killed as most human that enter into contract with devils usually fight for the demons. Up until now Favian has full control , in future though is unknown