Most things occur in threes. Three races of man, three races of ponies, three types of divine entities.There are planes of existance: Heaven, Hell, and the physical realms: Earth and Equestria.
There are also three things that make up a person. Wisdom, Courage, and Power.
The powers of Hell are on the rise as the Dragon King Satan is about to wage war on Heaven and the Earthly planes of existance. Only the combined power of Angels, Mankind, and Ponies can stop all Satan. An archangel returns from the physical world by unconventional means to help prepare the whole of creation in defeating this threat to creation. But will it be enough to save Heaven and the physical world?
The wisdom of the angels, the power of mankind, and the courage of ponykind are all that stand between universal destruction and a thousand years of peace.