The Black Fog used to be a pony but was were turned into fog and he resumed the name The Black Fog. He's a very dangerous villain who has the power to turn into a fog and no one can follow him in the sky. The Black Fog uses this for his own dark purposes. The Main 6 are the only ones who have the existing power to stop him. Or do they even have to stop him?

This includes some forms of ponies getting badly hurt. But I in my own opinion don't classify the story to be 'Teen' rated.