Shortly after Twilight's regeneration, the Doctor and her leave to adventure through time and space once again. This time, however, they're faced with an even greater task: discover the secret of the alicorns. How exactly does a unicorn become a god with immortality? How did Twilight, Celestia, Luna, and Cadence become so powerful that they could survive beyond death and become something greater? These questions nag at the Doctor as he and his faithful companion continue their adventures through time and space, saving lives and ending wars before they can begin.