It's night time, outside of the walls of Canterlot, Sombra wandered around the kingdom as he gave it a speech, "Equestria... you're suffering from this horrible disease. My wife, my step sister, and my nieces are spreading it to those weak minded fools. Other rulers have joined their sinister plot to end you. I, King Sombra, will end their madness once and for all. I will overthrow my wife, locked up the others, and bring peace to our new empire. Once it's all done, we shall have peace. No more pain. No more death. And no more lies. Just my complete power and love to you... my Equestria." After he was done, his smile faded when he sense something in the direction towards Ponyville. "I sense my daughter is endanger."
Meanwhile, at Ponyville, everyone was enjoying their time of peace since Twilight and the others bring peace once again. Then suddenly, everyone were alarmed by two ponies bursts out of the castle window. The two are Rainbow Dash and Starlight Glimmer, fighting each other. When they almost made contact to the ground, they both separate and levitate.
Starlight stare angrily towards her corrupted friend and demand, "Rainbow Dash, surrender now or I will no longer be holding back."
Rainbow Dash laughed, "Go on do it. Give in to your hatred. Just like in the past when you were evil." Starlight was disturbed by what she just said. "I know what you have done, Starlight. You went back in time and ended our friendship. You should have kept it that way. This should have been a peaceful world without these corrupted princesses ruling over us."
"Rainbow Dash, the outcome was darkness and depression. The future of these outcomes caused pain, suffering, and deaths. Twilight told me that the only thing is evil is the villains."
"WELL IN MY POINT OF VIEW THE PRINCESSES ARE EVIL!!"
"Whoever done this to you is filling your head with lies."
"How can I know if you're lying to me? I mean you were a villain and try to end our friendship. How can I know that if you try to get rid of me and take control of Equestria yourself?!"
"SHUT UP!!"
Starlight rushes towards the possess Pegasus, but Rainbow dodges her attack and grabbed her from behind. Then, she began to choke her friend. She whispered in the unicorn ear, "That's right. Use your anger to get killed easily. You're just like me, I always have a big temper. Now, get ready to die."
Suddenly, a rope was thrown around her neck and was pulled by the others, which letting the victim go. Sadly, Rainbow rid from the rope and tackle her best friend, Applejack. The sinister Pegasus began kicking the cowgirl in the stomach. Next, she was pulled back by Rarity and Pinkie Pie, but she easily escape and knocked both of her friends to the ground. When she spotted Fluttershy, who was horrified by this fight, she was about to harm her. Luckily, Starlight flew in and tackle her possess friend from hurting any more of her friends. The evil Pegasus tossed her friend off and started to beating her hardly. Then, Applejack kicked her best friend side, which pushed her away from Starlight.
As the possess rainbow pony slowly got up, Applejack shouted at her, "Give up now sugarcube! Ya don't want to make it worse!"
Rainbow laughed, "Why not. It's just got better all of sudden. And besides... when will I get another chance to beat the scrap out of you."
The cowgirl rushes towards her friend to ram her, leaving her wide open. Before Rainbow get a chance to strike, she was hold down by Rarity magic. Thanks to Rarity, Applejack rammed into her possess friend, which broken some of her bones. Unfortunately, the sinister pony still stand. Then, the evil Pegasus rushes towards the cowgirl, causing her to get ready for a kick. Suddenly, she tricked her friend and rushes towards the beautiful unicorn. She tackled and thrown her towards Applejack.
Before she finished her friends, Pinkie rushes to her and began chewing on her left wing. She even talk while chewing, "How you like this Dashie? It hurt does it. That's right, you can't handle the pain!"
Rainbow Dash pick her up and began spinning her around before tossed her aside. Out of nowhere, Starlight tackle her and try to rid this infection out of her. Sadly, the possess Pegasus punch her in the face and hold her down. She began punching her in the face furiously again.
Until, a voice she recognized cried, "RAINBOW!! PLEASE STOP!!" She turned and spotted Scootaloo right beside her with tears running down her cheeks. "RAINBOW PLEASE STOP IT!! PLEASE COME BACK TO US PLEASE!!"
She slowly got off of Starlight and began petting her young sister. She spoke, "Ahh. Poor Scootaloo. A young beautiful filly, who can't even fly yet. Ha Scootaloo." She picked her up. "How about we started training you how to fly."
Fluttershy, hiding behind the corner, know what she's doing and dashes to them. She cried to Rainbow, "Rainbow please put her down?! Don't do-"
"YOU STAY BACK!!" She slapped her best friend away from her, leaving a shock look on the young filly. She resumed taking her young filly towards the edge. "I had been training you for a while, huh Scootaloo?" The scared filly was nervous to respond, so she nodded. "Good. I think this time... you're ready to... FLY!!"
Then, she just tossed her own sister out of the castle and she's falling. Twilight screamed in horror, "SCOOTALOO!!"
Twilight quickly got up and rushes towards the falling filly. When she gotten outside, she dive down and try to reach Scootaloo, but she was too far away. Her was horrified because the young filly was about to hit the ground. Before she made contact, Starlight appeared below and caught the young filly.
Both of the mares stared at the poor Scootaloo, reimagined the terrifying close call. Twilight spoke to the young filly, "It's alright Scootaloo. You're safe now. It's alright."
Tears were running from the poor filly and said, "T-Thank you."
The moment ended when Rainbow Dash appeared and laughed, "HA!! That dumb filly can't even save herself! How sad is that!"
After they let Scootaloo get somewhere safe, both of the mares stood angrily against their possess friend after what she had done. Twilight spoken with hate, "That's enough, Rainbow Dash. We will defeat you here and now. You will fall!"
Both of them fired their magic at her, but she quickly dodges their blasts. The sinister Pegasus rushes towards them, but they both disappeared before she made contact. She tossed and turn, making sure where they are. Then, she was blasted from behind and landed to the ground. Twilight and Starlight both frozen her wings. Applejack thrown her rope around her again and Rarity tied her up.
The rageful Pegasus roared out loud in anger. While she was roaring, the whole citizens of Ponyville surrounded her and were horrified. Twilight and her friends stood in front of her and spoke, "It's over Rainbow Dash. You have lost."
The possess Pegasus kept struggling to escape, but she was well tie up. Applejack spoke, "Come on y'all, let's bring her inside and try to fix her up."
Before they move, they heard Rainbow started to cry. They draw closer to their possess friend, making sure if it's not a trap. Finally, she cried with tears running down her cheeks, "Please girls... please help me. I'm scare. Please help me. Please untied me... I think I can control myself now."
Pinkie Pie was excited after hearing her real self and shout with joy, "YAY!! We are so happy you're back Dashie! Don't worry I'll-"
Starlight blocked the joyful pony and spoke, "Don't fall for it Pinkie. Look at her eyes, they're still dark."
Then suddenly, she tossed her head as far as she can towards her friends and try to bite them. She roared in fury, "STUPID PONIES!! SOON ALL OF YOU WILL BOW DOWN TO MY FATHER AND HE WILL RULE ALL OF YOU PATHETIC SOULS!!"
"Father," Twilight said confused. "Who's your father Rainbow?"
"I WILL NEVER TELL YOU PRINCESS!!"
She walked towards her and demanded again, "RAINBOW!! WHO IS YOUR FA-"
Suddenly, a unexpected shadow surrounded Rainbow Dash and tossed the young princess aside. Her rushes to her aid and they watched helplessly as the shadow kept circling around their friend. Finally, when the mysterious shadow faded, the possess Pegasus disappeared as well. They were confused about what just happened. What was that shadow? Where did it come from? Most importantly, who's Rainbow Dash father? Twilight tell the others, "I have to report to Princess Celestia."
Somewhere in the forest, the shadow appeared again and appeared Rainbow Dash and her father, King Sombra. He stood silent over his injured daughter until she spoken. "I'm so sorry father. I've failed you."
He turned towards his daughter and lay his hoof on her shoulder. "Don't worry my dear daughter," he cheer her up. "It's all according to plan."
"It is."
"Why yes. You stroke fear to your pathetic friends. You also have shown the citizens of Ponyville that the Princess Twilight Sparkle is weak. I am so proud of you."
She was surprised by her father reaction to her mission. She bowed in front of him, "Thank you my father." She raises up, "What's my next assignment?"
"Your next assignment is to hunt down the ruler that stolen my rightful kingdom, Princess Cadance."
"How can I get to the Crystal Kingdom in a short amount of time?"
He draw his daughter towards a cliff and answered, "You don't have to go to the kingdom. Because..." He pointed towards a carriage headed towards Canterlot, with Cadance cutie mark symbol on the side. "...she's coming to you."