The Elements of Chaos have been awoken, and have consumed Twilight with their dark magic. With them, a massive army of shadow ponies has been awoken, and Twilight takes command of them. With this army, she plans to conquer all of Equestria. Will anypony be able to stop this fighting force, or will Equestria fall to the hands of the corrupted Twilight?
Doesn't become a tragedy or romance until later on in the story.
Map referenced for placement of towns, cities, mountains, etc and their names:
http://static2.wikia.nocookie.net/__cb20130403195245/mlp/images/c/cb/Map_of_Equestria_April_2013.jpg
Cover image by dreampaw on Deviant Art.
When Twilight stumbles on a secret room in the library, she finds a prophecy that will turn her world upside down.
After the prophecy has been fulfilled and the Elements of Chaos have been awoken, there is nothing stoping Twilight from waging war with Equestria, and the only goal in her mind is to conquer all of it.