Changelings are one of the most mysterious races known to Equestria. In light of growing unease, Twilight writes a treatise on all she knows about Changelings.
Every pony in or from Equestria has been yanked into Earth's ancient past - as dinosaurs. Scattered widely in time and space, will anypony be able to survive?
Forced to crash-land on a mysterious ring-shaped construct, the crew of [i]The Pillar of Autumn[/i] must rely upon the last known Spartan-II - and six top-secret Spartan-IIBs - for their survival.
After overhearing Shining Armour talking to a mare, Twilight Sparkle discovers that the nickname 'Twily' didn't originally refer to her - and that it wasn't originally a nickname either.
Eight months after the events of Equestria Girls 2: Rainbow Rocks, a new threat arises that not only threatens Equestria, but also every other dimension in existence - and it's Twilight Sparkle!
As Twilight wanders within the ruins of the Castle of the Two Sisters, she is blissfully unaware that she is about to discover a secret that has stayed buried for close to a millenium...and will change her understanding of Celestia and Luna - forever