The Cherokee legend of "Two Wolves" teaches of evil as eloquently as any story ever did. It is more clear than either Dr Jekyll and Mr Hyde, or Hulk vs Dr Banner.
Evil is born of emotional indifference, and this is why we are commanded to love.
Good and evil both evolve in our neurology and our cultures. Thus the first battle is firstly an internal one to become a real hero. The second battle is to alter the social ether to help others win their battles too. Evolve yourself. Then evolve culture to help others. We win or lose together.
The evil dark, not the noble dark, will come at you through your primitive drive. Any hunter will go for the weak spot of an animal, and that's yours, my love. First there will be a trigger to open up the primitive drive, activate it as fully as possible, then will come the impulse to cause harm, one that hurts both others and yourself. Your only protection is to love fully. Love yourself. Love others. Be present in the moment. Question your own actions - own them fully for regardless of the evil force, except in the case of true insanity, they are yours. And long after we have forgiven you, you will struggle to forgive yourself. If an action feels as if it comes from your survival drive, with a feeling of malice, hate or fear - stop. If an action feels as if it comes from your higher thinking mind and with a feeling of love, kindness and compassion - go.
The pathway into evil begins as small acts of cold heartedness, yet as with any journey those small steps become more significant as they add up. So, wherever you are on that pathway between love and indifference, start making choices for love while you still have enough soul to redeem.