Oh, well you see, Sweetie Belle is leading an invasion of the last earth kingdom stronghold, and it just so happens that Avatar Twilight is there to defend the city from the advancing nation. Oh, and there's also an epic and actually rather creative storyline before this moment that while taking cues from Avatar in terms of plot structure, is still rather cool for all the Not His Sled moments it pulls. Oh, and a lot of decomposite characters.



Though, I don't know how much you'll like it. The author writes Pinkie as VERY 4th wall aware. On the other hand, there is a real push to have dynamic characters, the action's fun, and it tries to merge the mythologies of both shows to create something better. Oh, and just like with your story, Discord is the final boss. (even though they're only 2/3 done) I think you'd like it.