One hundred years ago, Twilight Sparkle gave her life to defeat Grogar, the Tyrant of Tambelon. But legend says that she will return, in Equestria's time of greatest need.

Thunder Shield, the last survivor of a destroyed people, is Princess Luna's student, but he is morose and moody, unable to move past his grievous losses and afraid to form new bonds with other ponies. He opens his heart only to Princess Luna and to his fairy friend Kenzi, another orphan of the world who has no idea of where she came from.

When Grogar returns to wreak his vengeance, Thunder must thaw out his frozen heart and open it to other brave ponies if he is to stand against the cruel tyrant. With only a ragtag squad of Royal Guards and a time-travelling Twilight Sparkle to aid him, Thunder Shield must rediscover the magic of friendship to save Equestria from darkness and despair.