Many years ago, shortly before the birth of one Twilight Sparkle, Celestia, ruler of Equestria, found a small item in a forest. That item? An egg. Around the same time, Celestia, ruler of Draconica found something small in a forest. A pony.
Sunset Shimmer: Princess Twilight Sparkle's most faithful student. After bearing witness to the End of the World, she travels back in time to destroy the Dark Regalia and save her future. But a ghost from the past has other plans...
Twilight learns of Sombra's past, and finds him alive but weakened. She decides to learn how to use his Dark Magic for Good, by taking him back to Ponyville.