The battle against the Legion of Doom had an unintended consequence. The disruption caused to the world's magic has awakened an ancient nightmare from a time before ponykind.

The Shadow of Evil, Gyaos.

With the body count rapidly rising and quickly running out of ideas that won't risk more lives, the new Ruler of Equestria, Princess Twilight Sparkle must now trust to a guardian left behind in case Gyaos ever awoke.

The Last Hope. Gamera.