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"You could join us, Mabel. Wouldn't that be nice, to become one of the most feared, most powerful beings of the multiverse? You could do everything your heart ever desired." Dipper shouted, stepping closer and closer, each footstep punctuated by a word, his voice booming... It was a far cry from the preteen with insecurity laid into him.
The boy in the blue suit floated to the ground in an elegant fashion, commanding attention with just his confident smirk. He followed the gesture by putting out his hand and reaching to her, similar to the dream demon making a deal. Full of confidence in not only himself but in her decision. Bill chuckled happily from his throne, far enough from the scene as to let Dipper choose what he did without his immediate control, regardless of the fact that everything he did had been influenced by him in some way.
Mabel's eyes grew tired, her breathing shaky. She looked to her brother helplessly, with no help given, before setting her jaw. Her open palm turned into a fist, and her answer was obvious. "No, of course not."
In a split second of a moment, fog covered her eyes and obscured her vision. She coughed, moving to turn and run, held back by two hands made of a yellow-blue magic. Dipper held out his hand threateningly, tugging her to him simply by moving his hands. The girl took it into herself to shout, standing her ground and digging her feet into the ground.
"Stop struggling." He said softly, his voice coming out in a frustrated huff. "It makes it harder for me not to kill you this instant. I have to give you a second chance to answer, after all, you've always been emotional. I wouldn't want to kill my dearest sister if she had said no just due to some silly impulses of yours. I'll give you a second chance."
He brought his hand closer to him, and the yellow-blue hands pulled Mabel right to him. "So what do you say? Do you really think you'd rather struggle than join us?"
"Yes," was the only word she could say. It was bitter, the emotion that crawled up into her throat as she stared at her brother. She shot a glance at the Bill Cipher that was somehow so charismatic to so many people.
The Dipper she knew was gone. He had been captured by him one day, and he never really came home, even before Mabel was able to know that he was gone. She had assumed he had been home from an arduous mission when he had come home with blood stained on his shirt and different eyes, the ruthless eyes of someone who would do anything. She stopped herself midway a sob. She could have done something.
"Do you know what happens when you don't accept my offer?" Dipper smirked, his suit (obviously chosen by Bill) somehow reacting with his emotions to go from blue to a harsh red.
"What happens? Do you kill me, do you torture me like how Bill does?" Mabel shouted, pulling away from the hands as best she could. He only brought her closer, until she was staring him straight in the eyes. There was gold in his eye. It was beautiful, but it was hollow. She couldn't breathe, the more she stared at it. Gold, gold, gold. Another reminder of Bill's mark on him.
"Correct!" He almost enthusiastically replied to her question. Her eyes widened. He- he was actually- She only pulled away harder, screaming in utter hatred, a grave truth she had at some level known being confirmed.
Mabel put her hand out in the same way that he did, trying to make something, despite not knowing what to make. She had to do something, she couldn't let him destroy the world for a simple whim. She wouldn't let herself die.
"Magic doesn't come that easily to amateurs, Mabel." Dipper mocked her, chuckling as he spun his pointer finger around. She was shaken around and disoriented. "Can you feel it? The magic pulling you around and around despite how you may struggle? You can't do it just by trying really hard."
She stayed silent, thrashing violently at the hands with tears streaming down her face.
"Last chance, sister." He stressed the last word in a hiss. "You would be all powerful, you could learn to do what I just did to you, you could conquer universes, live forever, do everything in your biggest dreams!" He focused his sight on Mabel, suddenly looking as vulnerable as he had when they were still children. "You'd be happy."
"That- that isn't what true happiness really is!" Mabel cried, taking advantage of his split second of weakness to detach herself from the hands and to shout at her brother at the same level as him. "Happiness isn't brought by conquering worlds, and being mean, and stuff!"
She felt her heart crying out at her. "I know you're still Dipper! I know that you can change again... Let go of Bill. Come on. I know you're still the wimpy Dip-Dop who's obsessed with old pop songs, and cryptids, and-"
Bill narrowed his eyes and met Mabel's eyes threateningly. He stopped himself mid-action when Dipper began.
"I knew it. You don't understand." He laughed drily. "You know what Ford told me? He told me that I'm being manipulated by him. But you know what the thing is? I'm not."
"Dipper?"
"I'm happy! Really goddamn happy! He gave me what none of you were able to give me. I don't want to go back to before!" Dipper shouted, his voice cracking with every word. He shot a blue fireball at her and it missed. "I thought it'd be nice to have you join us. I spent time convincing Bill that you'd be great to have with us. With your creative, chaotic ideas, and your ability to push me to do things I wouldn't do otherwise. But more so, it was because you were my sister."
Mabel lost her spirit and lingered weakly, realizing the truth. The person in front of her wasn't her brother, and it was evident through the world around her. It was destroyed and barren, with monsters roaming it and humans assembled into a throne, of all things. "But you aren't my brother. So I'm not your sister."
Dipper ignored her words, biting his tongue painfully before he said anything stupid. "There were universes where you joined me. I visited a few, actually, where the three of us: you, Bill, and I conquer our world in murderous glee. I guess it was just blind hope that we could be like that. I should have known that of all of the versions of you throughout the multiverse, it would be mine that would say no."
He threw a fireball at her, and this time, it didn't miss. Mabel screamed and then she coughed, curling up into herself. Dipper tried to maintain a cool, unaffected expression, until he broke and gave an almost pitying look. He materialized and threw a spear through Mabel's heart, killing her immediately. It was a generous death compared to what he could've done.
"Goodbye, sister."