While researching cutie marks at Twilight Sparkle's library, the Crusaders find an ancient book of spells hidden in the floor. Naturally they open it.

Possessed by the dark magic of the book, the Crusaders use everything they've learned about the Mane Six over the course of the series to be surprisingly effective villains. The Mane Six and the Princesses meanwhile have some trouble adjusting to the idea of the Crusaders as dangerous enemies. What follows is a dark comedy.

[[http://www.fimfiction.net/story/51272/the-cutie-mark-crusaders-bring-about-the-apocalypse The Cutie Mark Crusaders Bring About the Apocalypse]] is a WesternAnimation/MyLittlePonyFriendshipIsMagic fanfic by [[http://www.fimfiction.net/user/BronyWriter BronyWriter]].


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!!This FanFic contains examples of:
* AffablyEvil: The possessed Crusaders just want to be left alone to complete their ritual. They can't understand why everypony is being so unreasonable about stopping them.
* BatmanGambit: The CMC figure that, once they have summoned the powers of darkness and gotten their cutie marks, the Mane Six and the Princesses will throw the evil back in its can like they always do. [[spoiler:They later change their minds about destroying the world, and by the time the summoning is complete, most of the "heroines" are [[TakenForGranite petrified]].]]
* [[spoiler:TheBadGuyWins: Oops.]]
* BilingualBonus: The requisite OminousLatinChanting is in Latin. Google Translate exists. Do the math.
* BlackMagic: Now, really, [[SarcasmMode who'd of thought an evil book of spells had evil magic]]?
* BloodMagic: Required by the summoning ritual.
* DemonicPossession: Just opening the book is enough to turn the Cutie Mark Crusaders into willing servants of evil; fully prepared to bring hordes of undead down on Equestria and [[spoiler: use Spike as a blood sacrifice.]]
* [[spoiler:DownerEnding: The Ancient Ones are awakened, and they destroy the clubhouse with the Mane Six and Crusaders inside.]]
* TheEndOfTheWorldAsWeKnowIt: The ultimate result if the ancient ones actually get summoned.
* EvilVersusOblivion: Discord and Nightmare Moon turn on the Crusaders for this reason.
* ExactWords: [[spoiler:The book promises great rewards for its users. It never says they'll get to ''keep'' those rewards.]]
* EvilIsNotAToy: Everypony else is desperately trying to convince the CMC of this. [[spoiler:They learn the lesson too late.]]
* FreakyFridayFlip: Discord inflicts this on the Mane Six. [[spoiler:Then their memories switch as well. It sticks.]]
* FromBadToWorse: The book transforms the CMC into alicorns. Then they awaken Nightmare Moon and Discord.
* GreaterScopeVillain: The Ancient Ones responsible for enchanting the book remain vaguely defined forces while the corrupted CMC [[TheHeavy drive the action]]. [[spoiler:They appear and are even given names at the end, taking over from the CMC as the {{Final Boss}}es, but they also refer to a "leader" who is never explained.]]
* OminousLatinChanting: See BilingualBonus.
* PragmaticVillainy: Discord and Nightmare Moon are aghast to discover the Crusaders are quite serious about summoning the ancient ones to destroy the world.
* [[spoiler:ShootTheShaggyDog: The CMC successfully complete the summoning in spite of everypony else's efforts, and the remaining heroines ''and'' the CMC die ineffectually.]]
* ShoutOut:
** The term "the Ancient Ones" is a reference to ''Film/TheCabinInTheWoods'', [[spoiler:and the very last scene plays out the same way as the movie's does]].
** Discord quotes [[TheseusShipParadox the ax riddle]] from ''Literature/JohnDiesAtTheEnd''.
** [[spoiler:The Ancient Ones]] tell the CMC that they [[Film/ReturnOfTheJedi "will pay the price for [their] lack of vision"]].
* TearJerker: [[spoiler: The ending. Not only do the CMC succeed in summoning The Ancient Ones and ending the world, but the initially heartwarming moment of the CMC getting to hang out with their big sisters one last time before they die is rendered moot when you consider the TheseusShipParadox and realize that it's not actually their big sisters, but the other members of the Mane 6 with their bodies and memories switched.]]
* TomeOfEldritchLore: What kicks off the plot and is the source of the conflict.
* TheseusShipParadox: [[DiscussedTrope Brought up]] by Discord (or rather, the axe variant), prior to [[spoiler:inforcing a FreakyFridayFlip on the Mane Six]].