Disclaimer: If I owned GF, everything would be gay.
Ever since coming to the small town of Gravity Falls, Mabel became afraid of the dark.
But it wasn't until that geometrical triangle monster who tried to enter and ruin Grunkle Stan's mind that she became afraid of the dark.
Sometimes when she was alone in a dimly lit room, she would get the feeling that she was being watched. And when everyone was asleep she'd feel vulnerable to the voices whispering and murmuring sweet goodnights in her head. When she finally closed her eyes, they were to be opened in a dream-like atmosphere. The place was very similar to her Grunkle's dreamscape. Only it was spectated in a vacant palate of monochrome.
Other times Mabel would try to stay awake and think of Sev'ral Timez songs to keep her mind occupied. And when Dipper asked why she looked so tired, she would reply with, "It's girl things, Dip." She knew for a fact that girl things and womanhood and everything and anything related to that scared her brother to no end.
When the creature stalking her felt bold, it would sometimes come in light, like when she was with Candy and Grenda or during a mystery. It would talk to her and she would accidentally say, "What?" out loud and then the voice would whisper;
"Your mind is playing tricks with you, my dear."
Mabel was convinced a ghost was haunting her with the intent to drive her insane.
But when she was alone and felt empty inside, the voice would talk to her and she would talk back as if having a normal discussion. A discussion with a twelve year old girl and an invisible devil plaguing her dreams and tormenting her.
Mabel would forget that the voice was a demon at those times. She found it to be a friend, almost like a second conscience. So she was startled when the voice slipped up and called her "his Shooting Star."
Finally she knew who it was. The same triangle monster who tried to cause chaos to her Grunkle Stan's mind. Bill Cipher.
When she found out it was him, she would sleep with Dipper in his bed and try to quickly pace to wherever there was light; sometimes under the lamp or outside in the sun. Mabel would never keep her mind vacant and devoid of thoughts. Wherever she went, she would think about her friends, parents, anything to keep her mind running. It would especially help to think about Mermando.
It would only become painful for Bill to enter her mind when she thought about useless things.
The familiar tug of sleeplessness entered Mabel's senses and that was really the only time Bill and her can interact without distractions. It would kill him to see his Shooting Star in a broken state like this. But it would also make him smile. To hurt a Pines, especially in the most painful of ways possible, sent a sharp stab of nostalgia Bill's way. The nostalgia would always make him gleeful with a grimace of pain.
The Pines. That family always made him uneasy. Uneasy, safe, they somehow managed to capture his trust in their own way. Capture his trust and lock it in a bottle where he can no longer get back. As if he belonged with the family but feel so out of place.
So when the demon finally got to Mabel, he had no idea whether to cause her more anguish or let her rest peacefully.
Either way, she'd be physically asleep without the fear of being awoken.
When he invited the girl into his monochrome dreamscape, she stepped in without hesitation.
Mabel touched the ground and glanced at her surroundings before looking back down at her feet. The same place every time she sleeps. The only was difference was the absence of the obnoxious voice of Bill Cipher that she grew used to.
It was odd. His voice was always in this place to guide her, she thought. …Do I have to find him this time…? Mabel, agreeing with herself, shakily walked in Bill's dreamscape; going into the black and white Mystery Shack.
She was greeted with the exact same appearance of the Mystery Shack Gift Shop. Except instead of any of the contents being monsters or mysteries, the jars and other areas were labeled. And as tempting as looking into the jar of "Fears" and room of "Futures" was, she suppressed the urge to look in. If there was anything she learned, it that privacy was an important priority. The mess she found in Dipper's search history had been horrific.
She shivered as something, it felt like a hand, clamped on her shoulder. It was gentle but Mabel couldn't shake the feeling of the malicious intent behind the gesture. When another hand, she was sure it was one now, glided along her hair she bit her lip. Everything felt so innocent but she was in a dark area with the exception of these hands.
But if there were hands, there had to be a body.
Mabel reluctantly turned slowly and came face to face with a tall blonde man. Said man's lips turned from a straight line to a smile too innocent to belong to the monster forming it. His head tipped to the side.
"Hey there Shooting Star!"
To say that Mabel was terrified was a complete understatement. She was petrified of the man—triangle—no, demon!—standing in front of her and her body trembling did not help anything at all.
Bill's innocent smile turned into one of amusement as he felt the brunette shudder under him. He still held onto a strand of hair, patronizing her.
True, he hated when the girl felt sad or disabled from lack of sleep but he loved to see the fear and confusion in her eyes as well.
To see someone so inferior and afraid of him felt like a lullaby, made him calm and happy. To see others in pain was euphoria for him. It was only different for the Pines family.
They made everything different. In good and bad ways!
He hated them all.
It was so fun to see the charming great niece of Stanford's trembling and staring up at him with round doe-eyes. Her curiosity would cost her dearly one day. Probably by his own hands.
Bill sighed and pulled the girl in a hug. Not now. He couldn't threaten Mabel now. To see her so scared was good for now.
"You should know, Shooting Star, that you are not going to leave anytime soon."
The trembling became larger magnitudes of shaking and Bill heard sobs. It broke his heart to see Mabel like this. But the pain of a broken heart is what felt the most amazing.
He pressed on, wanting to break her in a way that she could sense the false care in his words.
"It'll just be me and you here. The devil trying to shatter his shining star. He'll give her sweets, make her feel loved, then send her to the worst circle of Hell. The torture will be too much for the shattered star and she'll become nothing afterwards. Just a forgotten memory and dust in which no one will care for her.
"But not immediately. The devil will treat his star like the shining mass of fire she is. Build her up with friendly greetings and warm treats. Then extinguish her painfully."
Mabel shook her head in Bill's chest. Bill thought he heard the sobs turn into laughter. His suspicions were correct when Shooting Star decided to let go of him and clawed at his back.
"Oh Bill," she started, carefully laying out her words. "If only you knew."
It was the blond's turn to become confused. What did a dumb, little twelve year old girl mean by that?
"What?" Bill asked. He was skeptical. What did she know that he didn't. He was Bill Cipher!
"Nobody's going to save you." Mabel whispered.
Well, wtf did I even write, I have no idea. Here's my contribution to this fandom and blah blah Murry Christmas, Huppy Hannukah, Eid Mubarak.