Plot summary

In the magical Land of Equestria, at the capital city kingdom of Canterlot Castle, Princess Twilight Sparkle and her best friends, that form the Mane 6 (Applejack, Rarity, Rainbow Dash, Fluttershy and Pinkie Pie) and Spike the young purple dragon, are getting ready for the new annual Friendship Festival. There, Twilight is feeling overwhelmed organizing the event as the Princess of Friendship, especially since her fellow princesses, Princess Celestia, Princess Luna, and Princess Cadance, decline her more grandiose proposals. However, her friends sing a song to encourage her. With such support, the festival gets underway.However, an invading fleet of dark storm airship blimps led by the villainous renegade unicorn, Tempest Shadow, soon arrives and demands the Ponies surrender. When the Princesses refuse, as Tempest had hoped, her forces quickly attack overwhelm Canterlot's defenses including magically freezes/encases almost all the Princesses in stone. Twilight almost shares that fate, but for Rainbow Dash saving Twilight just in time while the cross-eyed Pegasus, Muffin Hooves, sacrifices herself taking the blow, providing a critical few minutes distraction for the Mane 6 to escape.Twilight and her friends escape after hearing Celestia's last words to Luna "Go South past the badlands to find the Queen of the Hyppo-" just before she is cut off just as she is petrified to stone. Twilight thinks they need to find the Queen of the Hippos, and set off while Tempest learns of their escape.After an arduous trek through the Equestrian desert badlands, they find a forbidding desert city called Klugetown. It has many monsters that sell other animals and after Pinkie Pie, against Twilight's advice, foolishly calls attention to themselves to request help, the Mane 6 are surrounded by the denizens of the city desiring to exploit them. However, a charming and sly fox-like humanoid cat called Capper comes and saves them. After secretly arranging a message to be sent to a creditor that he will have something to offer to settle his debt, Capper lures the Mane 6 to his home offering to help them both considering shelter and claiming to have information about the location the "Hippos" they seek, over Twilight's suspicious objections about trusting a complete stranger.Once there, Rarity, the most trusting of all of Capper, surprises the cat by repairing and improving his suit, in an act of selfless generosity he cannot comprehend, while Twilight finds a map showing that it is not the Queen of the Hippos they are looking for, but the Queen of the Hyppogryphs. Realizing that Capper was being untruthful to them, Twilight's suspicions are confirmed when Capper's creditor, a mole-like creature named Mr Verko, arrives to take the Mane 6 into slavery as recompense for Capper's debt. Meanwhile, Tempest has arrived in the city in pursuit of the princess, and arrives at Capper's house seconds after his creditor did.As Tempest violently subdues the criminal when he attempts to enslave her, the Mane 6 flee in the confusion until they reach the airship docks and desperately stowaway in a departing delivery airship. Meanwhile, frustrated at her quarry escaping again, Tempest demands that Capper tell her where the Mane 6 are going. Although obviously frightened by Tempest's threats, Capper is reminded by Rarity's repairs to his coat of how goodhearted the Mane 6 are and confesses a false destination to throw Tempest off their trail. Unfortunately, Tempest forces Capper to accompany them to prove his story true.On the airship, the Mane 6 are discovered by its crew of humanoid parrots under the command of Captain Calaeno. They crew is just about to toss them overboard when the lunch signal is sounded and they immediately break to have lunch with Mane 6 invited to the table. Moving past this strange professionalism and generosity, Rainbow Dash finds out that they used to be pirates before the mysterious Storm King forced them to become delivery birds. Delighted to meet actual pirates, Rainbow sings an encouraging song that restores the Pirates' mojo and they throw off the shackles of their servitude to the Storm King. However, at this exciting development, Dash overdoes her adulation over Twilight's objections and performs a Sonic Rainboom, a bright rainbow colored shock-wave, that alerts the pursuing Tempest of their position.Tempest and her crew overtake and board the ship and threatens the pirate crew to surrender the Mane 6. Hiding in the hold, Twilight finds a way to escape by having everyone drop down a bottom hatch and barely assembles a makeshift balloon for her flightless friends as they fall. Meanwhile, they see that the pirate ship is destroyed above them presumably with the crew and Capper.The Mane 6 land and continue the journey to the Queen of the Hyppogryph's castle, which is supposedly on Mount Eris. They reach the castle only to find it completely abandoned and they hear a singing voice coming from inside the castle. They creep past the rubble to an interior pool and get there just in time to see a glowing shape slip inside the water. Pinkie Pie dives under and comes back up with no news of the glowing shape, before they can get out of the pool however, they get sucked in and almost drown.They are saved by the same glowing yellow shape which blows bubbles of oxygen around their heads and they are brought to the underwater palace of the Queen's the princess is the glowing shape and she introduces herself as Princess Skystar and the Queen is Queen Novo, Queen of the Hyppogryphs. They turned into merponies when The Storm King tried to steal the pearl that gives them the magic to turn into merponies. They turn Twilight and her friends into merponies and Twilight tries to plead Queen Novo to let her borrow the pearl so that they can turn everypony in Equestria into merponies to fight the Storm King. Despite, Princess Skystar's excited pleas to participate, Queen Novo refuses and the ponies get ready to leave.Then in sheer desperation, secretly Twilight comes up with a plan to steal the pearl away and she manipulates Pinkie and the others to go distract Skystar while she does so. Later, Queen Novo comes and sees Skystar making good friends outside the palace and she is about to help them when an alarm rings. Furious at what Twilight was attempting in return for her hospitality, Queen Novo takes away their merpony magic and banishes the Mane 6 at the surface sputtering and splashing.Now seeing all their efforts have been in vain, Twilight's friends are angered upon realizing that she used them for a scheme that would have been unnecessary if she hadn't ruined things. At the end of her own patience, Twilight angrily rants that her friends' collective stupidity throughout this quest left her with no alternative and she has had enough of their incompetence. Deeply offended, Twilight's friends outside of Spike angrily abandon her and Twilight is left alone deeply regretting her her temper and her failure in her mission.However, her funk is quickly interrupted by Tempest Shadow who captures her. Securing her in a magic-proof cage, Tempest sings a song to her about the real world and the backstory of Tempest's life as a filly plays while she sings. Tempest explains that she was a happy filly until an attack by an Ursa Major (Lunas Bear) scarred her and broke off her horn, leading her to be rejected by her peers and embittered. Thus, she now serves the Stormking who has promised to restore her horn if she helps him gain the power of the Princesses of Equestria.Meanwhile, Twilight's friends get over their bitterness and are about to talk to her when Spike comes running about her abduction. Now, desperate to help Twilight, their despair at their helplessness to do so is relieved when Skystar appears, still eager to help. Furthermore, the Pirates and Capper arrive at the moment, having somehow survived Tempest's wrath to offer to help as well.Twilight is taken back to Canterlot where she sees everypony is enslaved and/or caged. For instance, she sees the sing, Songbird Serenade (Canterlot's pop-star Pegasus), trapped inside a cage trying to sing, but silenced every time she tries, she lowers her head in shame and is brought to the throne room. Taken to the palace, the Storm King arrives, revealing himself to be a Grey lightning-powered powerful ape-like faun monster. and in his rage complaining about the castle's cute aesthetic, he stabs his staff into the floor and it absorbs the magic form all four princesses.Meanwhile, Capper is able to smuggle the Mane Six and the Pirates into Canterlot with a giant Trojan cake. However, they are spotted by Tempest's hedgehog sidekick Grubber and must fight the Storm King's minions. Eventually, the Pirate tell the Mane 6 to get to the palace while they keep minions busy.As the Storm King enthusiastically revels at the incredible power he now has, Tempest reminds him of his bargain with her. However, the Storm King admits that he was using Tempest and has no intention of upholding his end of the bargain. At this betrayal, Tempest tries to fight but is instead zapped towards the railing where she clings on for her life as the storm/whirlwind rages around the castle. After freeing herself, Twilight has to pick between taking the staff from the fallen Storm King or saving Tempest. Against her apparent better judgment but with her conscience, Twilight decides to save Tempest to the renegade's shock.Then, the Storm King gets back up just as Twilight pulls Tempest up and he gets ready to zap them with his newly enchanted staff. At this time, the Mane 6 shoot themselves to the castle with Pinkie's humongous party cannon and they knock the Storm King over just as he is about to blast Twilight and Tempest. The staff is about to be pulled into the storm outside and zaps the roof, causing it to crumble, Twilight and her friends are trying to get to the staff before the Storm King and they succeed causing the Storm King and Twilight to hurtle into the storm.After an agonizing few seconds, Twilight returns unharmed with the staff, though, and the friends embrace. However, while they are embracing, the Storm King crawls back up the railing and gets ready to encase Twilight and her friends to stone with the power ball that zapped the other Princesses into stone. Tempest jumps in front of them, saving them, but the spell also backfires and hits the Storm King, petrifying him into a statue which meets doom as it smashes apart in the resulting fall (although he is not strictly "dead"). However, Twilight and her friends save Tempest from the same fate and they free her and the Princesses.Together, Tempest and all the princesses magically restore Equestria's magic and the Friendship Festival resumes in light of this victory, this time with all the other new friends they have made. They have their party and Songbird Serenade sings her new single "Rainbow" with friends are rewarded such as Capper getting a stylish top hat and cape ensemble from Rarity in light of his heroic efforts helping them.During the celebration, Twilight tells the now forgiven Tempest that she is already very powerful, horn or not and invites her to stay in Equestria. Moved by Twilight's offer, Tempest at least uses her still considerable magic to make the light show the Princess of Friendship originally wanted. As they then move to join the festivities, Tempest quietly tells Pinkie Pie her real name 'Fizzlepop Berrytwist' and Pinkie Pie ends the movie by joyously shrieking how wonderful that name is.