Once upon a time, a pack of diamond dogs hunted a mortal pegasus mare through an underground labyrinth of metal and stone. They hunted her, caught her...only for her to be rescued by a prince out of a fairytale.

Fluttershy is more than a lost little filly in the subway. One of the former Keepers of the Elements of Harmony, gifted with magical Sight and a talent for helping all creatures great and small, she has lived her entire life fighting for the lives and livelihood of the creatures of Ponyville and the Everfree Forest. Though her family thinks she's crazy for living on the ground and focusing on "earth-bound pursuits," though her dedication to her calling has cost her a great deal in her life, her heart remains true to her cause.

Prince Enbhárr is the exiled heir to the throne of Eimane Ablach, the Emerald Empire in the magical otherworld of Antequus. A scarred and broken heart masked by a scarred and bitter shell, through centuries of grief he has come to believe that mundane ponies are irredeemable; for the sake of his people, the ponies of the mundane realm known as Equus must be exterminated.

Then, one night, compelled by honor and memory, Enbhárr rescues Fluttershy from a pack of diamond dogs. Injured in the fight and on the verge of death, he has no choice but to trust in his enemy - an enemy that treats him with impossible gentleness - to save him. And in learning to trust each other, Fluttershy and Enbhárr will embark on a journey that could change the fate of mortal and immortal ponies alike.