Over three months ago, Twilight was given three amazing gifts for learning so much about friendship: A pair of pegasus wings; the title of princess, like Celestia, Luna, and Cadence before her; and the responsibilities that come with the title, though Twilight would rather rule Equestria at the safety and comfort of the Golden Oaks Library in Ponyville. Unfortunately – and ironically, fortunately, at the same time – Twilight did not attain immortality, and will inevitably die of old age with her friends. This is why, when the time comes, Twilight must adopt and raise her own successor to the throne of Equestria, as Celestia did when she adopted and raised Twilight.

Princess Celestia eventually knew this, as well. So, she assigns Twilight a new assignment: Train herself for the time she must train her own student. And, what better training-wheels to use than her own friends? However, this training isn't just normal training; it's also combat and weapons training, where Twilight's friends inherit spiritual weapons from within their Elements of Harmony, and must use them to defend Equestria under the lavender alicorn's leadership.

Around the same time, another nation of ponies threatens to wage war with Equestria…