Generations ago, the Sliver of Darkness was sealed away by Twilight Sparkle. Now, it has resurfaced in modern Equestria, bringing unparalleled darkness with it. Bridlewood has been laid to siege. Zephyr Heights guards a dying pegasus. And Maretime Bay swirls with a dark power unlike any seen before.

Corrupted by the Sliver of Darkness, Sunny Starscout is unrecognizable as the mare who united Equestria. Now calling herself "Eclipse," this new threat will stop at nothing to gain the power she needs to destroy everything her friends hold dear.

Twilight Sparkle has fallen to a great darkness. Now, the remaining Guardians of Friendship must face their former leader in an all-out war. Can Twilight Sparkle be saved, or is she beyond the reach of her friends forever?