Twilight Sparkle is called away to tend to Luna when she falls ill. As Luna grows sicker and Twilight more determined to help the younger princess, she begins to uncover dark secrets about the elements, the alicorns, and her own past.
Twilight fights against sinister manipulations, struggling to overcome a deep-seated darkness within. As she battles to preserve everything she cares about, she will sacrifice anything necessary to succeed. But the price of victory may be herself.