To understand that there isn't some mastermind of evil is a difficult thing. It's a release of decades worth of belief, it's the sheer terror of understanding that all ones ever known of evil cannot simply be cast on to something else (or another being) that all of that evil resides within. The thing that eventually calms the soul is an understanding that there is only 1 true God. The creator. If there were to be some kind of Evil that was so powerful that he could match God's might then God wouldn't be the architect of everything but that he would not only the only God. God is good, but without evil can there be good ? Would good disappear without evil ? These are the philosophical platforms that have plagued man since we were created.