Two-thousand years of Equestrian history through the eyes of those who lived it; from Princesses Celestia and Luna's mentorship under Starswirl, to the first appearance of Discord, to the sacrifice of The Pillars, and Luna's banishment. This story fills in the gaps of the show's canon (ignoring comics and other media).
Extended Universe:
Chapter 11 -> Flight of the Valkyrie
Chapter 14 -> TBA Starswirl/Pillars Spin-off