Gideon Gleeful lit the last of the candles before shaking the match to put it out. "Y'think that code's safe in your lab, Stanford?" he sneered, opening the journal to the page indicated, rereading through the instructions and incantation. "Well, we'll see what my new minion has to say about that."
He fought back a twinge of apprehension and made sure his Latin pronunciation was up to snuff before continuing.
"Magister signum, Ego instigo vos, Ego autem venio ad signum insolutam dimittit, solvere!"
He felt a clenching in his gut and a sensation of having the breath drawn out of his body, dropping the journal and doubling over, feeling a jerk as a rift of SOMETHING was opened from his body as a conduit, his mouth opening almost against his will as he began stammering gibberish. "SDROW LACISNESNON, SDROW LACISNESNON, SDROW LACISNESNON, SDROW LACISNESNON, SDROW LACISNESNON!"
A light flashed before him, and a shape that vaguely resembled a pine tree opened up in the air. A large yellow eye opened in the center and giddy, almost insane laughter rang out as something vaguely humanoid formed from the hole, pitch black save for the eye, and stood before him.
The figure stood upright and stretched, looking around. "Oh wow, Gravity Falls, it is GOOD to be back!" he exclaimed, the blackness fading to show what looked to be a humanoid teenager with long limbs and spiderlike hands, still looking almost humanly passible, save for the huge eye on his forehead. He honed in on Gideon, grinning with sharp teeth. "Name's Dipper. And I'm guessing you're some kind of little disfigured troll." He snorted at the insulted look the boy gave him. "I'm just kidding, I know who you are, Gideon!"
Gideon backed up slightly. "How…how do you know my name?!" he demanded, clenching his hands nervously.
"Oh, I know lots of things." Dipper's grin almost took up his entire face, his large eye closing and two smaller ones opening, flashing images so fast Gideon almost couldn't comprehend them. "Lots of things." His eyes closed and his singular eye snapped open again, his grin becoming more normal. "Hey, look what I can do!"
He turned to a doe that was snuffling around at the edge of the clearing, his spindly fingers dancing slightly. The doe jerked where it stood, its body shifting to become taller and broader, antlers bursting from its head as it almost violent reformed into a buck, shaking the blood and flesh from its new antlers.
"Genetic codes are still codes, you know. Cool, huh?"
Gideon jerked back, his eyes wide. "You—you're insane!" he stammered.
Dipper snorted. "Sure I am, what's your point?" He waved his fingers again, the antlers on the deer falling off and its body becoming smaller until it was a doe again. The doe turned tail and sprinted back into the woods.
With the horror gone, Gideon clenched his hands, mustering up his nerve again. "Listen to me demon! I have a job for you! I need you to get into Stanford Pines' lab and get me his book of codes!"
Dipper rolled his eye at such a mundane task he'd been summoned for before pausing. "Wait…" He turned his back to Gideon, frowning. "…Ford Pines…" His singular eye closed and the other two opened, images of a six-fingered man coming out of a portal, playing D&D& More D, climbing into an old space ship, being turned into a gold statue flickered over his vision.
He closed his two eyes, opening his one, turning back to Gideon. "You know what, you've convinced me, I'm sold!" He walked up to Gideon, looming over him with a creepy grin. "I help you with this, and you can help me on something I've been working on. We'll work out the details later."
"Deal!" Gideon said without hesitation, holding out his hand. Dipper's grin grew broader, holding up his hand and encasing it in a blue flame, shaking Gideon's hand and enveloping both their hands with it.
"Welp, time to invade Ford's lab!" Dipper chirped, turning on heel. "This should be fun. Remember—reality is an illusion, the universe is a hologram, trust no one!" He stepped out of the clearing and vanished as soon as he entered the borders of the forest.
As Gideon stood there pondering over what even Dipper had said, Dipper took one step out of the clearing and exited right into another, this time where a large, cozy house was situated, the outside unkempt and decorated with a variety of satellites and transmission objects. Dipper snorted, slipping his hands into his pockets.
"Wow, Grunkle Ford, how predictable can you get?" he muttered, glancing skyward as though speaking to a deity. Which he was, in a sense. "Welp, I've got a code book to steal and your mortal paradox twin to have fun with. Hope this one likes D&D& More D."
He headed up to the house, one hand slipping out of his pocket and rolling a 38-sided die between his fingers.