Celestia is in grave danger.
Suddenly alone, Luna must struggle to get her bearings and keep the kingdom together in her older sister's stead, with little knowledge of the society that moved on without her in a millennia of imprisonment.
Somewhere lurks an enemy, powerful and unknown, with malevolent intentions for Luna and her now slumbering sibling. Dark forces stir, schemers are setting plans into motion, and amid it all the night remains permanent though not by Luna's choice.

The Moon Princess intends to make her sister proud. That is, if she can keep herself together -and alive- long enough to see it through.

The longest, darkest night of Equestrian history has just begun.