Darkness is not a thing. It is a lack of something (Light). Darkness can't overcome the Light unless the Light dies. His Light is Infinite and Eternal and no Darkness can withstand it. Darkness exists only because He allows us free will. He wants us to turn to His Light of our own free will so that means some will choose Darkness. However they are numbered and His Host is infinte. The Host draws it's power from His Infinite Power. The Darkness only has the power that we give it through fear, anger, and all the other negative emotions. Be of the Faithful and the darkness will have no power over you.