Hey guys! Natflash here again, bringing you another oneshot!

This was a request by Lady Zia, so I hope this works for you! This is actually kinda like two oneshots in one, so, WHOO! BONUS DEAL!

Once again, Disclaimers! Dun Dun Duuuun!

I do not own MLP:FiM, Or Gravity Falls. They belong to their respectful owners.

The only thing I can possibly own is the AU!

The Nightmare Returns

Summary: Princess Mabel finds her brother has taken on a new form, determined to overthrow her and make the night last for all eternity.

Rated: K+

It was the middle of the afternoon when it happened.

Princess Mabel was enjoying Mermando's company in her pink and white bedroom, laughing at each other's jokes and stories when one of the royal guard came in, in his traditional golden armor and blue helmet plume.

"Your Highness," He started, just poking his head into the room. "I hate to disturb, but someone would like to see you in the throne room." That was all he said as he vanished and closed the door behind him.

"It's alright, my love." Mermando said. "I'll wait for you a thousand years if I have to."

"Aww, Mermando!" Mabel said, grinning, her hair gleaming in all its different colors, magnifying her chocolate locks running down to her back. "You're so sweet! I'll be back quick, Ok?"

She blew him a quick kiss and left the room. As she walked down the white hallway pillars, she thought about who would possibly need to see her. She thought it was probably just a commoner who requested something, and nothing more.

So it was quite a surprise when Mabel entered the throne room and no one was in sight.

"Hello?" She called throughout the darkness. "Anyone there? Dipper, is this some prank?" She carefully paced her step in the large room, torches smoking from last night. He golden sandals made hardly any mess on the floor, and her short but very pretty white dress sparkled against the stained glass windows.

"Not… another… step." A voice called from the darkness, making her jump in surprise and whip around. She heaved a sigh of relief as her brother emerged from behind his throne, his cape the same as always and his navy robes fluttering from the small breeze in the room.

"Oh, phew! There you are, bro! I was getting worried! What are you doing in here? Why'd call me?" She smiled as always, but her brothers face was a mask of solemnness, his voice as chilly as a winters breeze.

"Did you really except me to sit idly by while they all basked in your precious light!"

"B-bro? Dipper, what're you talking about?" Mabel was confused. Precious light? What was Dipper doing? Her eyes followed his as he walked to the space between the golden and silver thrones, each representing the twos respective time of day.

"There can only be one true rule of this land! And that ruler… Will be ME!" Dipper screamed, slamming his fists down on the brick layer, showcasing a sun and moon, shattering it to pieces. His eyes glowed a brilliant white, making cracks form on the wall and eventually reaching the large stained glass window, before it breaking open. Mabel had to shield herself from the large glass shards that were sent flying every which way. Dippers face showed total rage and anger, his hands glowing a silver-blue as his powers raised the moon, eclipsing the sun, sending beams of black light everywhere.

Dipper, too much for him, fell to the ground, before a red ball of pure energy swallowed him completely.

"DIPPER!" Mabel screamed, concerned for her brothers safety. She tried running up, but the sheer magical power sent her flying back.

The ball of energy was wrapped around by a black shadow, fading into a blue color. It burst open to reveal a totally different Dipper.

He still looked the same, maybe a little paler than normal, but his dark robes turned into armor the color of the sky, his navy wings now pitch back. His crown was gone, but in its place was a helmet with three curved points on his back, like crescent moons. His once light blue cape was replaced with one that looked like the night sky. His eyes snapped open, revealing bright blue, snakelike eyes. He laughed maniacally, revealing his sharp teeth and slightly deeper voice.

The moon stayed up in its place, but the sun vanished from all sight, as Mabel looked in total horror at her brother, before trying to put on her brave face.

With a look of desire, he shot a beam of bright blue energy, dragging it up the ceiling, making rubble fall and a plume of dust rise up, making Mabel cough and sputter as the beast of her brother slowly advanced towards her, daring her to make a move.

She spread her large, white wings, attempting to stop her brother, but with one shot from his palm, she flew down with a thud, and with her voice breaking from desperation, tried to reason with her now insane brother.

"Dipper, I'm not going to fight you! You gotta lower the moon, bro! It's your duty!"

Dipper seemed shocked for a moment before recovering. "Dipper? I am… Nighterror Nebula!"

Mabel had a look of pure horror on her face, seeing her brother was beyond reason. She noticed his palm charging up again for an attack.

"I have but one royal duty now… TO DESTROY YOU!"

It was over.

…

The Nightmare was over...

...

Mabel was back, the Elements of Harmony restored, and Nighterror Nebula was gone. Mabel was happy to be back, thanks to the help of six kids (whose names will not be mentioned.), and she was thankful that the nightmare was over.

"And now," Mabel said, looking over by the cracked wall which Nighterror Nebula was defeated. "If only another will as well. Prince Dipper."

Sure enough, the Prince of the Night was laying down, his wings covered in small bits of rubble, glass, and armor pieces. His crown was on his head and his robes and cape were back, and his face was, thankfully, his normal color. He struggled to get up, his teal eyes shrinking in fear at the girl, fearing his judgment day was upon him.

"It has been a thousand years since I last saw you. It's time we put our diffrences aside. We were meant to rule together, bro! Will you accept my friendship?"

Poor Dipper stared at the floor, tears brimming on his eyes, standing up slowly before rushing over to Mabel and gripping her in a death hug.

"I'm sorry, Mabel!" He said, his crying making him slightly hysterical. "I- I- I promise I won't do s- something like that e- ever again!"

Mabel was also on the brink of tears, though not afraid to let them fall.

"I- I missed you to, bro."

AWWWW! THAT MOMENT WAS TOO SWEET!

I love stuff like this, especially when Dipper apologizes to Mabel in Sock Opera and Luna to Celestia in MLP. Don't you?

Oh, and if your confused on why I cut off the epic fight, don't worry! I'm saving that for another oneshot, and I'm gonna make it even more epic.

Well, hope you enjoy, and send in those requests!

Oh, and pick up your complementary Prince Dipper action figure on your way out! The wings actually move!

Oh, yeah, and Favorite, Like, and Review! It means a lot!