Princess Lun, the guardian of the night, pesot rules over Equestria alongside her big sister. When the Cutie Mark Crusaders suggest she should have a holiday as equally prestigious as Celestia's Summer Sun Celebration, she declines. Luna isn't comfortable with such attention-especially after all the terror she caused as Nightmare Moon. So when she realizes Celestia is orchestrating a surprise festival in her honor, she decides to have some fun and take matters into her own hooves. What's a princess of darkness to do?