Celestia and Luna have been gone for hundreds of years. How does Equestria fare under Twilight's rule? Is it still a kingdom of magic and friendship or has it become something else entirely?
Princess Twilight transforms into the Nightmare after a nervous breakdown, and it is up to her friends to fulfill the elements of harmony to save Twilight from herself.
What if during the Summer Sun Celebration, Twilight didn't meet the rest of the main six? What if she met different ponies? What new things would she learn from these different ponies?