Somewhere in the Nightmare Realm, two dark creatures, one in the shape of a pyramid with one eye and another of unknown appearance, worked together to make the most powerful force imaginable. She was created and named Obscurial.
She was made up of power from the two beings who made her. From the one eyed pyramid, Obscurial gained the power of almost everything. Weirdness was her specialty, though. From the creature with an unknown appearance, she gained a special type of power. She became one of the few people to be able to travel between dimensions without a portal or gap between universes.
Obscurial was very gifted, indeed. Since she gained the ability to change appearance from one of her creators, the pyramid named Bill, she would always make herself look like a girl with long, wavy light brown hair, that seemed to turn gold on the ends. Her eyes, a beautiful shade of green, with golden specks.
Sadly, she was used as a slave to Bill, who would always use her to travel to different universes. There was only one he couldn't get into though, even through something as powerful as Obscurial.
A few Earth years ago, Bill was banished through memory erase. He was almost a goner, until the being with no appearance showed up and saved him from certain peril.
This being's name was Abosco, and he was the only known dimension hopper, or someone who can quickly travel to dimensions, before Obscurial.
Abosco was just going to Earth to get something, when he suddenly saw a shriveled up Bill, mostly dead, but not quite. Humans could not see him because he Abosco has no appearance. Bill, could see him, because he is a very special type of being. Abosco, being a generally nice creature, helped out Bill and brought him back to his home dimension.
Abosco had always longed for a child, someone who could share his special ability. He knew Bill would be able to do something like that. After they both created Obscurial, Bill fought off Abosco and stole the child, using her for his own liking.
Abosco still hasn't recovered fully enough to go and get his child back. Besides, the only power he had was dimension hopping. Nothing useful for combat.
We officially start our story with a 3 year old Obscurial, but she makes herself 16, because she likes being what is considered a teenager on Earth.
Obscurial has always had a strange addiction with Earth, most likely because it is one of the only dimensions she has never visited, because her maker, or as she calls him, father, is unable to go there. She always asks if she can go, but Bill tells her she can when she's older.
Today was going to be the day Obscurial would ask her father if she could go to Earth. "Father, may I please go to Earth this time?" she asked.
"Actually, that's what I wanted to talk to you about," Bill said, anticipating Obscurial. "I want you to go to Earth and kill someone."
"What! You know I'd love to go to Earth, but I could never kill someone!?" Obscurial was obviously upset.
"Obscurial Imperi Cipher! You are meant to kill. Your first and middle names almost translate into dark power in Latin. You are a Cipher. Cipher's cause madness and weirdness. You will do this mission, or else!" Bill was really pissed off at Obscurial now.
"Fine! Only because I love you," Obscurial wasn't even sure if she meant it.
"You have four targets. All related. Stanly, Stanford, Dipper, and Mabel Pines. They are the reason why I can't go to Earth. I shall get my revenge on them," Bill tells his daughter, "Oh, and Dipper and Mabel are your age, too. Maybe you can befriend them, then kill them!" Bill wanted to drone on and on about them.
"So you're saying that I have to kill two teenagers! How old are the other two, anyways?" Obscurial exclaimed, appalled.
"Well, the other two are a couple of old geezers, but they do know how to put down a good fight. But I have a perfect plan to kill all of them," Bill responed.
Obscurial longed to go to Earth, but taking another person's life seems like a big price to pay for simply visiting somewhere. She looked away from her father's cat like eye as he spoke, "So, when you go to Earth, you turn into what you are right now. A beautiful human teenager. You will go to Dipper and Mabel's school in California. I already bought you a place down there with my infinite wealth. You make Dipper fall in love with you, travel to Gravity Falls with him in the summer, then kill them all. Sound like a plan?"
"I dunno…" the frightened girl replied. She didn't possibly know how she could live with herself if she ever did that to one innocent human, let alone four! Despite her thoughts though, she knew her father would not allow her not doing it. "Guess so," she replaced her unsure words with, although her thoughts were more unsure than her words.