Celestia fears Sunset Shimmer has joined with a dark power from Earth. She entrusts her prodigy student Twilight Sparkle and her friends with the task of apprehending her and bringing her back to Canterlot for questioning and trial. The mane six will face many challenges as they journey to Earth in hopes of stopping this evil as the armies of Equestria mobilize for war.

Five years after the Plot to over throw her, feeling they could be reformed, Princess Celestia grants a pardon to the surviving members of the sinister shadow cult, on the condition they renounce their evil ways. One of those released from the dungeons is Twilight's estranged twin brother, who wishes to make peace with her. Meanwhile, darkness of the shadow gathers around them.

While most ponies in Equestria believe Blue Blood is nothing more than a vain, selfish, snob, he is secretly the heroic Dark Alicorn, defending Canterlot and all of Equestria as its greatest unsung champion.