Discord had one last trick up his sleeve to play before being locked up again: he's turned Equestria's timeless protector into its most dangerous threat. The kindhearted princess that ponies loved and adored is gone, replaced by an alicorn of iron and blood that forged Equestria out of the fires of pre-history.

Can Twilight Sparkle survive being the student of a pony who never had need of the magic of friendship or will she be forced to sit on the sidelines as Equestria irrevocably changes around her?