The Nightmare Dimension is a kaleidoscope of colors. He's not stuck here forever exactly, but visiting the human world is challenging and costs a lot of magic. A demon (or any other supernatural being) needs at least a shred of a physical form. Bill could always possess someone's body, but even demons have to follow strict rules.
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Bill's bored of the unreal. He sighed and looks at the letter in his hands. I really don't want to attend this party…
Everyone else's accomplishments are greater than his.
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Ghastly and bizarre monsters circle an elegant table. Blood-colored tea is poured into translucent tea cups. It smells like iron. Cursed flower petals float on the surface. A scorching, decaying taste is typical for demon brew.
"Fashionable as always, Bill?" A demon with a thousand eye stalks and an overbite cackled.
"Yet you're not even a fraction terrifying."
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Furiously, he glares at the partiers. Cipher's mantra is substance and style over unsophisticated scariness.
"Yes tell us," a demon whose voice sounds like a bell asked. "How is your world domination going?"
"Why ask?" A four-headed monster dips an arm bone in his drink and eats it like a pastry. "His last apprentice almost killed him after stealing his powers. It was a weak human!"
"Weak?" Another scoffed. "Ford was annoyingly smart but he's more of a demon than Bill is!"
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A demon's goal is to cause chaos, rule the world, or destroy it. Beings that are wild and brutal, they endlessly search for something fulfilling to do. Living thousands of years gets boring. Bill and others who live in the Nightmare Dimension make bets to see who can change the most worlds.
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"I've started a zombie apocalypse. Despair is my favorite flavor."
"Cliché! On a desert planet I summoned a flood. Now the human population is stranded in warfare for territory and resources."
"On two planets and three moons people build statues of me and sacrifice others for good luck."
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Cipher's eye lands on the putrid drink of blood. His reflection harbors bitterness and hatred.
Pathetic. Small. Powerless.
I should ditch these losers and host my own end-of-the-world party.
Still, Bill wants to outshine them. He used to be feared and intimidating –years ago. Back when humans were merely tribes. Chuckling silently he realizes this must be how Dipper feels. Both demon and human's outlooks are cast by how their peers define them –substandard, unimportant, and laughable.
No more.
They're underestimating me but they won't again.
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Floating back to his dimension, Bill's thankful for the eternal soundlessness for once. I wonder how Pine Tree is doing.
Cipher knows Dipper has made friends with the blonde girl –Northwest? The pair is going to cause chaos in Gravity Falls. Good. Things have gotten too boring lately.
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The demon feels subtle changes in Gravity Falls. Snaps of humming and crackling magic. Corrupted beings are gathering into an army. For now, it's experimental and provisional.
Bill wants to tell Dipper about Ford but if he gave him all the answers, he won't adapt and get stronger. Dipper has to fight his own battles in the future.
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It's amusing watching the Pines family train for combat. The scientist is shaking fearfully as he aims the bow –and misses. Stan scolds him by slapping his shoulder but then the two laugh. Mabel is shooting magic at targets and Dipper hesitantly tries to wrestle Stan. The old man's telepathy makes him almost undefeatable.
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Bill?
Night's darkness wraps Gravity Falls in a peaceful din. A wolf howls and crickets chirp. Warm lights from the Mystery Shack are obscured by shadowy trees. Bill teleports to the mindscape and bows.
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"I want to learn dark magic."
The demon's face fell from dazzling to somber. "You sure? It isn't a cakewalk."
"If I have talent for it I can't just let…let my dark magic disappear." Dipper grinned lopsidedly but there's a glint of seriousness. "I told you I want to be the strongest mage. And there are big mysteries in Gravity Falls. I want to know what's going on. Nobody will give me any information so I'll look for it myself."
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Cipher chuckled. Few ever show such scary dedication or heart. "You know, demons and humans aren't so different. We're outcasts. Overlooked. We want to shine but harbor a hint of lively darkness. Okay. Let's change the world, Pine Tree."
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Pines crouched into a fighting stance. "What do I do first?"
"Dark magic is raw emotion and energy but can be deadly cold and dangerous. Focus with will and strength." Wooden dummies sprout from the ground. "The first spell of dark magic is possession."
"Possession?"
"Usually it's easier possesses a living thing like animals but I know you humans have ugh," Bill shuddered. "Good hearts. So try and use the spell on these dummies."
"Uh…" Dipper blinked and flailed his arms. Nothing.
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Bill sighed. "Tap into your emotions. I know you're more of a thinker." Just like Ford had been. Though super intelligent he had a hard time casting any spells except telepathy. "Focus on anger. Or something terrifying."
Dipper instantly remembers all the bullies from school. Mabel had been there to scold or distract them but when she wasn't, their torment was painful.
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Always bigger and stronger. Their venomous grins fixed a permanent frown on his face. They would make fun of him for being smart and then threaten him to do their work for them. For years Dipper was isolated from others and nobody wanted to be friends. How he hid in the library to avoid black eyes and bleeding wounds. Dipper felt like an ugly monster, unwanted and discarded.
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He loves books and their exquisite worlds much better than his own. But Dipper always desperately searched for confidence, something he could never assemble. It should've been easy.
When he'd cry, he wondered if things would've been different if he were a bit more antagonistic.
Bad people always win, don't they?
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Screaming, the mocking bounces in his mind like an echo in a cave, and he flings his arms. One of the wooden men goes flying and violently hit a tree. Bill cheered. "Whoa! Now that's dark magic! But let's see if you can control one of them."
"Making them move like a regular person?"
"Yes." The wooden men are reset to their original stances.
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Dipper knows the human body is made up of muscle that mimics plant's structures. Agile, but easy to break with enough momentum and strength. Plants are sturdier though.
I guess reading those books about plants was valuable.
He stares at one wooden man. His fingers twitch as he tries to grasp strands of magic in the air. The dummy flinches. It takes a step. Shadows flicker as Dipper struggles to tug at the magic –the dummy trembles and collapses.
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Bill hovered down to study the damage. "Okay. We'll work on that. Next is another spell. Sapping energy. You can absorb another person's stamina temporarily." He pokes the wooden fakes. "I made these with magic to mirror humans and they have human energy in them. You got this, kid."
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Lunging, the shadows followed excitedly. Pines punched a dummy and felt something like light rain hit his senses.
It's just enough that when the dummy's arm swings he's able to leap out of the way. "Did you see that?!" He laughed.
Bill nodded. "That's just a fraction of what dark magic can do. Let's see if you can withstand fighting." Twirling his cane, two dummies start moving. "Don't overuse those spells. Think of this like a real fight."
Dipper grinned.
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He runs, faking a punch, only to throw his hat onto its face. Spinning, he uppercut the enemy and it fell over. Ducking, Dipper dodges punches and a sweeping kick. He's constantly looking around and eyeing the wooden humans warily. Pines grabs the metal knuckles Stan had given him and faces the closest wooden dummy.
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Sputtering, Dipper fell. Mud and scars dapple his clothes and face. His muscles tremble and ache. He can't take another step. The only thing keeping him up is sheer stubbornness. Dipper refuses to quit.
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"We'll conclude here."
"No," he shook his head. "I won't…won't-"
"Taking breaks are vital. If a mage overdoes spells they'll get injured and-"
Pines is coughing violently. He feels something jammed in his throat, reaching from his lungs and twisting out of his mouth. Roots. Flecks of dirt and stone drop on the earth as Pines claws fearfully at his throat. The roots reply by entwining between his hands as if a snake latching onto food.
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Can't breathe! I can't breathe!
Bill quickly muttered a spell. Fire scorches the roots which become ash. Air crashes through his lungs. He takes deep breathes and then pukes small roots. All he can taste is burned bitter herbs.
"You okay Dipper?!"
"I…I think so? Lightheaded. That was terrifying!"
"It's a side effect when using too much magic."
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"I'm sorry Bill. I suck." Dipper feels like a failure. He practiced casting magic for hours and hardly could move one wooden fake.
"What? Don't be sad! Soon you'll be an extraordinary mage!"
"You think I will?"
Bill elegantly bowed. "Visit anytime and we'll work on those spells. Go rest. Your mana and strength will return."
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The grey mindscape faded back into color as Dipper marched to the Mystery Shack.
Bill is hurled back to the Nightmare Dimension. He knew something dire is going to happen in Gravity Falls. It's been years since the last war. Ford must be restlessly effervescing underneath the surface of wherever he is, waiting anxiously to try and destroy this world again. It was a miracle that the demon survived his last battle with the corrupted mage. He hopes that by being stranded in Dipper's mindscape and becoming his magic guide, he'll avoid death again, and live long enough to defeat Ford. Because both their worlds are counting on him and the Pines.