Why did she choose them over him? The question haunted the Didact, last of the Forerunners, even has he slept for untold millennia. The Mantle was to be the responsibility of every Forerunner, including her. Yet she forsook her duty as both guardian... and wife to save her precious pets. In the aftermath of his attempt to Compose her children, the Didact is haunted by that question again. And after all this time, he believes he has finally found the answer.

In a far-off corner of space, another librarian is tending to her own duties. Twilight Sparkle and her friends have been invited to Canterlot to celebrate Princess Luna's first birthday since her return, not knowing that a guest is about to show up uninvited...