Over 1000 years ago, the being who would one day be known as King Sombra was named Archmage Saros. In his laboratory under the Crystal Empire, he performs magical experiments and studies the book of dark magic given to him by his master Grogar. He focuses on his wrath to fuel his powers. He knows that right now, he's the weakest of Grogar's students, but that can change. Already his experiments have increased his size, given himself fangs, and given him incredible physical strength. After deciding it wise to keep the book concealed, he copies its contents, plus a few spells he thought up on his own, into a smaller notebook that is easier to carry.
Weeks later, now calling himself King Sombra, he takes over the Crystal Empire and murders Princess Amore and her husband Bene Lyric. He attempts to kill their infant daughter, but King Caesar, in the form of a Diamond Dog, battles him. Caesar bites Sombra's horn clean off, crippling him with pain, but his magic surges out of control and injures Caesar. As Sombra collapses from the pain, Caesar limps away and escapes with the baby and Sombra's notebook, which he had dropped during the fight. Sombra focuses on his wrath to dull the pain and repair his horn. He absolutely hates the baby, the reminder that some other stallion got to sleep with Amore instead of him. He casts a spell to bind the Crystal Empire's fate to him, and angrily declares that until Amore's daughter is dead, no one will ever have this empire without him.
Just over 970 years later, King Caesar is walking forward and he doesn't know how long he'd been doing that. He remembers briefly losing consciousness on the edge of the empire and had been in something of a daze since. All he knew was to keep moving forward to keep Amore and Bene Lyric's child safe. At least the infant in his arms had stopped crying. He's not in good health however, as Sombra had stabbed and blasted him with dark magic. But he presses on despite knowing his time is short before he needs to hibernate, trying to find the alicorn sisters, Clover the Clever, or anyone to care for the infant. It starts raining and he shields the future Princess Cadance from it with his own body. The shisa's attention turns to Sombra's notebook, which he'd grabbed on his way out to try and deny Sombra use of it. Spiteful and grieving, he tries to destroy it. But after an extended sequence of attacks, he fails to destroy it. Frustrated and blaming himself for Amore and Lyric's deaths, Caesar throws the book away and collapses to his knees, stoically crying as he's caught in the rain. Cadance, disturbed by the noise, starts clinging to him for comfort. Caesar slowly holds her close and picks himself up, stashing Sombra's book in a tree and resolving to come back for it after finding someone to care for the infant. Unfortunately, he didn't manage to come back for it.
Years later and a filly aged Starlight Glimmer walks into a darkened thrift store. Making her way past the selection, she's there looking for anything to help her learn magic in the hopes she could go to the School for Gifted Unicorns to reunite with Sunburst as Sunburst's parents sent all their magic guides with him. To her joy, she finds a magical notebook in the back authored by Archmage Saros himself, not knowing Saros was actually who became King Sombra. Elated, she sees it as her ticket to getting back to her friend and buys the book. To her frustration however, Starlight's attempts to read the book all end in failure as there is an enchantment on it that keeps scrambling the words and letters into incomprehensible gibberish. She throws herself at it for days and gets increasingly frustrated. The threat of isolation from her friend, anger about her denial of so many things in life, buck the trend of a recluse she knew she was growing into, and she sees this book as keeping her from everything she wants. She lashes out in rage and throws the book around her room, denting the ceiling, and huffing for breath after the outburst ends. When the books falls down in front her however, her wrathful magic resonates with the book. To Starlight's astonishment, she can now read some of the text and finds a magical suppression spell. She starts reading more text as it comes to reveal itself.
Two months later, Starlight stands before several teachers at the School For Gifted Unicorns as she must pass an entrance exam. Her older sister Moonbeam and Sunburst's parents are there to cheer her on, though she's sad when she doesn't see Sunburst. Also in the audience are Fancy Pants and Captain Stalwart Sentry, who had become friends of her family after saving her and Moonbeam from the dragon, as well as Stalwart's son Flash, who is around her age. One of the teachers is a little suspicious because Starlight has not earned her Cutie Mark yet, suggesting Starlight delay her test until she does, but relents and says if she passes, the school will not take it easy on her. Instead of the usual "hatch a dragon egg" test, Starlight opted for a demonstration of her magic. Starlight is annoyed and angry at that teacher, seeing her as looking down on and pitying her. As she fires her first spell, her anger takes control.
Starlight runs out of the city, trying to hide and suppress her magic, as her horn is uncontrollably firing dark magic blasts and creating Aerenth crystals everywhere. After hiding in some ruins, she frantically flips through the notebook and tries to find out how to turn her powers off. Tears fall from her eyes and only her willpower stops her horn from warping like Sombra's. During her test, she concentrated her anger and power, but when nothing happened after about two minutes, one teacher awkwardly started to say maybe they should let the audience out so that she wouldn't be so nervous. However, Starlight misinterpreted that and assumed the teacher was failing her. She lost her temper and fired a laser from her horn that punched right through the walls and ceiling. As the audience panics, Moonbeam tried to go to her, but Fancy Pants grabbed her and pulled her away while Stalwart did the same to Flash. The teachers called to Starlight to calm down, but she sees the teacher who doubted her and feels vindictive. She fires the magical suppression spell at her flank, thinking if the teacher would give her grief over not having a Cutie Mark, she doesn't deserve one either. The teacher screams in pain as her Cutie Mark starts to come off, but Stalwart suddenly slashes the magic beam in two with his lance, cutting off the spell, and yells that that's enough. He calms himself and tries to approach her, but a terrified Starlight teleported away and ran.
Starlight finally finds a spell in the notebook that induces a state of Tranquil Fury. She casts it and finally gets control of her magic, but she's exhausted and can feel her raw emotions behind a mental wall, ready to burst. Moonbeam catches up to her and carefully says it is okay. Starlight cries and Moonbeam hugs her. They may be sisters adopted by Sunburst's parents, but ever since their parents died, Moonbeam has been her mother for all intents and purposes.
In the present, Moonbeam Glimmer sips tea and reads a newspaper while sitting in her home. The headline is of Godzilla Junior turning back to his true form and entering the ocean. Princess Celestia assures the population that he's on a mission and they are not in danger. Other parts of the paper talk about Moonbeam badmouthing Junior the other day. Moonbeam is ashamed that she did that. She did that because she equated Junior with the dragon who killed her parents and now she knows that is wrong. Junior may have forgiven her, but she decides she has to make it right by finding some way to help him. The doorbell rings. She assumes it's the mailpony who has been flirting with her, but she is shocked to find it is her sister Starlight Glimmer. Starlight stoically enters the house and calls her "Sister."
Deep in his chamber, Grand King Ghidorah meditates. Gravity inside goes crazy and pieces of obsidian orbit his body. The many ponies he abducted are trapped inside an energy dome within the chamber. While he normally enjoys hearing his victims cry, scream, and beg for release, he can't afford to be distracted, so he makes them fall asleep. He is concentrating his formidable psychic powers to try to see the future. He's seen the past before, so he's convinced the opposite is possible. His warping the gravity has dilated time within the chamber, speeding it up so that a long time will pass for him while a short time passes outside. He has a blurry vision of a being of destruction facing against Bagan. The vision ends and he decides he's almost out of time. He needs to perform his mission. He goes to Bagan's chamber.
Enjin, who is currently possessing Sunset Shimmer's body, enters Canterlot by train. Enjin alters her body's appearance every once in a while to ensure it is not being followed. It scans the city and senses Princess Celestia is alone. It considers trying to attack her and claim her energy, but decides it is too risky and continues with its current mission. It explores the city and finds near the border a completely ordinary looking stone that houses part of the spell that prevents Changelings from entering. Enjin rips the stone out of the ground and drains its energy, opening a hole in the wards. Suddenly, it looks toward Hollow Shades, as it can sense someone with Grand King Ghidorah's energy coming towards the city (Starlight Glimmer). It also senses someone observing it. It quickly moves back into the city and alters its appearance again. The one spying on it is the Pony of Shadows/Nightmare. She doesn't know what Enjin is or what it just did, but she considers it a threat to its plans. Luckily for her, her former host is approaching by train.
