Just so you guys know, this is a Gravity Falls and Fullmetal Alchemist crossover. Set after the events of Gravity Falls. No traditional fma characters but gf characters take their places. Mabel is Edward (I'll explain how), and Dipper is Alphonse, also Mabcifica, (Pacifica is Winry, once again, I'll explain). Basically, it's a retelling of Fma Brotherhood, though there may be some Anime elements as well.

On with the Story! Hope you Enjoy!

Chapter One - That Fateful Night

A crow cawed in the woods of Gravity Falls, Oregon. It was in the dead of night and a storm was coming. Down in the basement of the Mystery Shack, two siblings gathered ingredients for an experiment. The first was a girl with brunette hair and honey golden eyes about 15 years old, the second was a boy the same age as the other and had the same brown hair and golden eyes. These were the Pines twins, Mabel and Mason "Dipper" Pines. Mabel read each one of the ingredients as she checked them off.

"Water: 35 liters, Carbon: 20 kilograms, Ammonia: 4 liters, Lime: 1.5 kilograms, Phosphorous: 800 grams, Salt: 250 grams, Saltpeter: 100 grams, Sulfur: 80 grams, Fluorine: 7.5 grams, Iron: 5 grams, Silicon: 3 grams, and fifteen traces of other elements," she recited.

"Ok, so we have all the ingredients," Dipper said, "Now for the constructional formula."

Mabel picked up the piece of chalk to her right and began to sketch out a large circle on the cold, stone floor. Dipper picked up another and started on the circle too to help speed things up. After about twenty minutes, Mabel finished up the circle with some finishing touches. She looked over at her brother and saw that he was looking rather uncomfortable.

"Don't worry, Dip," she consoled, "Your calculations are perfect, we'll see mom again soon."

Somehow that didn't help much, he still looked nervous but at least he was a bit more anticipating. Mabel stood up and walked over to the table, and began dumping all the ingredients into the large pan sitting in the center of the circle. Once she was finished, she grabbed the knife sitting on the table and pricked her finger.

"And finally," she said, holding out her finger over the pan, "some soul data."

She handed the knife over to Dipper who did the same thing. They placed the knife back on the table, and kneeled at the edge of the circle.

"Ready, Dipper?" Mabel said with a grin, her braces long since gone.

"Ready as I'll ever be," Dipper said with a nervous smile. The shadow of the suit of armor looming over him darkened his appearance, as if he could fade from existence altogether.

They activated the transmutation circle together and it lit up with a brilliant golden light, the ingredients began to swirl and bubble. However, the light in the room shifted from a gorgeous gold to a violent violet. The two siblings looked around the room confused. Dipper turned to his sister.

"May, something doesn't feel right," he said. Just as those words left his mouth, a crack was heard and Dipper lifted up his hand to find only a stump. He screamed.

"Dipper!" Mabel cried, but then felt a sharp pain in her ankle that made her fall to the ground with a grunt. Twisting her body around, she saw tiny black hands eating away last her left leg, her eyes widened. "A- a rebound??"

"Mabel!" Dipper screamed. Her head snapped up to see her brother being deconstructed right before her eyes! He reached out to her, and she grasped for his hand. "Mabel, help! SISTER!!"

"Mason!"

(Line Break)

Suddenly, Mabel found herself in a white void. There was nothing to be found in all directions except for a large stone gate looming over her from behind. On it, a diagram that all alchemists were familiar with, the symbol of alchemical knowledge itself carved into it, the Alchemical Tree of Life.

"Hello."

Mabel wiped around, coming face to face with a strange being, which was saying something considering she's been through Bill Cipher's weirdmageddon. The being had no features, and looked like a silhouette of her. There was no hair, no eyes, no nose, had a wide grinning smile, was completely white like the void around them, and had a black aura surrounding it which was the only thing separating it from the background. Mabel tilted her head to the side.

"Who are you?" She asked.

"Oh! I'm so glad you asked," god, damn thing even sounded like her. "I go by many names, I am the World, I am the Universe, I am God, I am Truth, I am All, I am One, and I am also You"

The large door behind her creaked open with a low and terrifying groan. She wiped around and stared into the abyss, and the abyss stared back with a large, singular, gray eye. She backed up, readying herself to high-tail it out of there. The same black spindly arms shot out of the door and grabbed onto her, dragging her inside. She screamed and fought against them.

"You have dared to knock on the door, and now, the door is open."

She fought harder.

"Quiet, child, this is what you wanted right? I shall show you, The Truth."

The doors slammed behind her as she took basically the acid trip of a lifetime, but ten times more terrifying and painful. It felt like all the information in the world was being downloaded into her brain all at once. It hurt, bad.

"IT'S TOO MUCH, IT'S TOO MUCH, MAKE IT STOP!!" She screamed. She felt her very body being deconstructed from the sheer power of the Gate. Even Bill Cipher wasn't this powerful! "WHAT'S HAPPENING TO ME?? STOP IT! MAKE IT STOP!"

Suddenly, it all became clear. The truth, of everything.

"Mom! Mom please!!"

As quickly as it started, it was over. She was back in the void, the only thing keeping her company was the being known as Truth.

"How was it?"

"I see," She muttered, walking towards the Gate. "So, Dipper's theory for Human Transmutation wasn't wrong, it can be done, it's possible… It's still just missing something!!" She turned back to Truth, who was now standing. "You have to show to me again, please!!"

"I can't do that," The being said. "I've already shown you all I can for the toll you paid."

"'Toll'? What toll?"

"This," Truth held out their left leg and it began to flesh out as hers disappeared. "Surely you knew."

"A-ahhh!" She gasped, as she stumbled on her one foot. Truth appeared right in front of her.

"It's the Law of Equivalent Exchange. Right, Young Al-chem-ist?"

All of a sudden, she was back in the basement.

(Line Break)

Alchemical energy whizzed through the air and the smell of copper and iron filled the room. A transmutation circle could be seen on the floor with a large pan in the center of it with a horrifying, cobbled together, and haphazard attempt of creating a humanoid creature inside it. All the while, Mabel Pines, clutching her leg, was lying on the ground, screaming in pain thanks to the missing limb gushing blood. Her brother, Mason "Dipper" Pines, was nowhere to be found.

"Dammit," she cried, "This, this can't be happening! It can't be! This wasn't--! This wasn't supposed to--!! NO!!! HE'S GONE! WHAT HAVE I DONE??!"

She fell to the side, crying. She managed to lift herself onto one arm, and looked up at the creature she created with a hopeful gaze.

"Please, Mom," she pleaded to no one. "Mom, plea--!"

The dust cleared as a horrifying creature that was not even human stared back at her. The thing lifted up an arm as it tried to reach out to her, it took a single ragged and uneven breath before its arm fell to the ground with a fleshy thump.

"No," Mabel whispered, "this… this is wrong. This, This isn't what we wanted!!"

She hung her head and cried, calling out her brother's name, "Dipper, Dipper, DIPPER! MASON!!"

She glanced over at the armor in the corner of the room, it will have to do until she can fix this.

"No, dammit." Mabel growled, she was pissed off now. "You're not going to take him too!"

She knocked over the suit of armor and the helmet flew off. Using her own blood, she drew a transmutation circle on the inside of the armor while calling out to Truth.

"Give him back," she demanded. "Whether it be an arm or my other leg, or even my heart, you can have it!! Just give him back, HE'S MY LITTLE BROTHER, HE'S ALL I HAVE LEFT!!!"

With a resounding clap, she sacrificed her right arm and bound her brother's soul to that armored body.

(Line Break)

The elder Pines twins raced down to the basement when they heard their niece and nephew screaming. The scene they happened upon was not what they expected, and somehow it was worse than the worst possible situation. The younger Pines twins told them about their experiment, which was why Ford even let them use the basement in the first place, so when they heard the two teens screaming, they thought something went wrong and the creature they were making was attacking them. Instead, they see a dead humanoid creature in the center of the circle. A living suit of armor without it's helmet and a strange symbol written in blood on the inside of the suit was holding onto Mabel who had two missing limbs and Dipper was nowhere to be seen. They assumed that this night couldn't get any worse, but when the armor spoke, their worst fear came true.

"Please… Help her."

The armor was Dipper.