The Demon of Sunset's Nightmares
Sunset Shimmer put on Twilight's crown and transformed into a demon. Demon Sunset was pure evil, but much less intelligent. She planned to take over the world with an army of teenagers, and tried to kill Twilight Sparkle. This was unsuccessful.
Twilight Sparkle and the human counterparts of Rainbow Dash, Fluttershy, Applejack, Pinkie Pie, and Rarity blasted her with a rainbow powered by the Elements of Harmony, exorcising the evil from her and returning her to human form. Remorseful for her actions both before and after turning into a demon, Sunset apologized and became friends with the five girls who had helped Twilight reform her and would later become a band called the Rainbooms.
What Sunset didn't know is that the evil inside her had not been destroyed. Demon Sunset was now a completely separate entity of her own, hidden inside Sunset, waiting to torment her.
A few days later, once all the damage to Canterlot High had been repaired, in part by Sunset to make up for what she had done, Sunset was having a slumber party with her new friends.
The girls were making good conversation, when suddenly, the room went dark, and a demon appeared. She had red skin, glowing green eyes, red batlike wings, fiery spiky red hair, and a red and yellow tail.
An actual tail, not the hair extensions that Twilight and the Rainbooms got when they transformed.
This was Demon Sunset. Sunset Shimmer's demon form had appeared before her.
"We meet again, Sunset Shimmer!" said Demon Sunset.
"No... it can't be!" said Sunset. "You... you're not real! I turned into you, and then my friends turned me back!"
"But I'm still here!" Demon Sunset's eyes and hair flared up. "You can never get rid of me! I am a part of you forever!"
A light shone from her forehead, and the Rainbooms fell under her spell.
"Now, my army of teenagers... Take over Equestria!"
"Yes, Master!" moaned the Rainbooms.
"No... Go away!" said Sunset.
Twilight Sparkle appeared. "I defeated you once, and I can defeat you again!"
"Now you don't have your friends to protect you!" said Demon Sunset, and she shot a fireball at Twilight. In a burst of flame, Twilight was reduced to a pile of ashes.
"NOOOOOOOOOOO!" said Sunset.
"Yes!" said Demon Sunset. "You are nothing! I am superior! And I will control you again!"
Sunset jolted awake in her bed, her hair frazzled from tossing and turning in her sleep. Breathing heavily, she looked around for her demon half, who was nowhere in sight.
"It was just a nightmare... She's gone, Sunset. You're not her anymore."
"Oh, just you wait," said Demon Sunset deep within Sunset's subconscious, even though she knew Sunset could not hear her. "I will torment you until you give in to me!"
When Sunset next saw Fluttershy she gave her a big hug, reassured that she was not under a demon's control.
Sunset had nightmares about Demon Sunset several times a week. They served as a constant reminder of her dark transformation. At times she was concerned that Demon Sunset might really live within her somewhere. She shook off the thought every time. No. She was the demon, and her magnified evil side had to have been erased. Besides, who wouldn't have nightmares like that after turning into something so evil and terrifying?
It didn't help that none of the students except the Rainbooms were willing to forgive her. None of them wanted to go near the meanest girl in the school who had become a demon that had brainwashed them to try to take over another world. She was never going to live this down.
"A demon. I turned into a raging she-demon."
It wasn't long before a new threat emerged: The Dazzlings. They put everyone at Canterlot High under their spell except for Sunset and the Rainbooms. Twilight Sparkle returned, and they tried to think of a plan for defeating the Dazzlings.
Having a slumber party at Pinkie Pie's house, Twilight and Sunset stayed up late, discussing how much they didn't want to let people down who expect things of them.
"I better get some sleep," said Sunset with a yawn after a cameo by Maud. "Good luck with the counterspell. Not that you'll need it. This must be nothing compared with the stuff you're expected to deal with as a princess in Equestria." She started to walk away.
"Sunset Shimmer?" said Twilight.
Sunset stopped in the doorway.
"Never mind. It's not important."
Sunset awkwardly grinned at Twilight and walked out the door.
Once laying down, she fell asleep quickly. She dreamed that Twilight and the Rainbooms were singing a song trying to defeat the Dazzlings, while she stood to the sidelines. It seemed to be working. The Dazzlings were looking weaker, and Celestia, Luna, and the students at Canterlot High looked like they were coming out of a trance.
"You did it, Twilight!" said Sunset. "You defeated the Dazzlings!"
Sunset ran towards Twilight, but she didn't seem to be getting any closer.
"Oh no, not again!"
"Yes, it's me again!"
Demon Sunset appeared, towering over them. She put everyone except Sunset, Twilight, and the other Rainbooms under her spell, not a minute after they had been freed from the Dazzlings' spell.
"They're all yours, sirens!" said Demon Sunset. "I've brainwashed them to feel SO MUCH HATE that you can become unstoppable!"
Adagio Dazzle, Aria Blaze, and Sonata Dusk sucked massive amounts of hate energy from the crowd into their pendants. Their eyes and pendants glowed a bright red, and then, in a flash of dark light, they transformed into reptilian creatures resembling ponies, but with tails in place of legs.
"At last, our power has returned!" said Adagio Dazzle. "Now we shall take over Equestria!"
"Here is the pathetic princess that tried to stop you!" said Demon Sunset, picking up Twilight by her hair and holding her in front of the sirens, while waving her other hand at the other five Rainbooms, who disintegrated. "Do with her what you will!"
"I think we will!" said Aria Blaze, and the three sirens flew at Twilight menacingly.
Demon Sunset turned toward Sunset. "You made all this possible! The sirens won because of you!"
"No... This is just another nightmare!"
Sunset woke up. She was relieved that this nightmare was over, and that she hadn't seen what the sirens did to Twilight. But, she was worried about what would happen with the Dazzlings. Would she screw everything up? Could she really give the sirens victory by accident?
No. It was impossible. Twilight knew what she was doing. She'd defeat them easily. She was a princess of Equestria.
She stood on the sidelines as Twilight and the Rainbooms battled the Dazzlings together with their song, but the Dazzlings were too powerful.
"Sunset Shimmer! We need you!"
Sunset was nervous. It all came down to her. Would she screw it up? Would she turn into Demon Sunset again?
No. This was the power of a song to counter the Dazzlings. She had just brought the Rainbooms back together when they had drifted apart on their own. This was the exact opposite of what she had done before. And now they needed her.
Sunset removed her jacket and began singing.
"You're never gonna bring me down! You're never gonna break this part of me!"
Sunset was activating a magical power. This was Demon Sunset's chance. She tried to take control of Sunset.
But something was wrong. It wouldn't work. Sunset was too confident that she could help her friends. Demon Sunset had no control over her outside of her nightmares. Yet.
Together, the seven girls unleashed the power of their song and destroyed the Dazzlings' pendants, taking away their power and ability to sing. Their threat was over. They would either live the rest of their lives as ordinary teenage girls, or age into dust having lost their immortality as humans for over a thousand years.
That night, Sunset dreamed of relaxing with her friends in a peaceful, magical forest.
Demon Sunset appeared. "How dare you resist me? I am part of you! You will never control me!"
"I won't be haunted by you any longer!" said Sunset, facing the demon head on. "Go back to where you came from!" She raised her arm and shot a blast of red energy at Demon Sunset.
Demon Sunset shot a fireball to counter, but Sunset's blast vaporized it effortlessly and hit Demon Sunset directly. Rays of light shone from Demon Sunset and she shattered to pieces.
"Way to go Sunset!" said Rainbow Dash. "She was no match for the real you!"
The nightmare finally ended. Though she knew it was only dream counterparts of her friends who stood before her now, she enjoyed the rest of this peaceful dream with them.