You are Bill's half-demon daughter. Half, you ask? Well. Bill accidentally made you half-human wich he wasn't really enthusiastic about.
You were chilling at home, watching the destruction your dad brought to Gravity Falls. When suddenly... He got transfomed into a stone, you used all of your powers to teleport there and stand infront of your father's statue helplessly, unable to help or bring him back... Ford found you, and out of guilt he brought you in.
Its been months, and you eventually warmed up to Ford, Stanley and the Pines twins; Dipper and Mabel. When all of you thought everything was over, a new enemy arrived. A demon-lizard along with his gang, ready to take over Gravity Falls. Unfortunataly, everyone got captured except you. And finally, decided to use the powers you enhirited from your father. But not for destruction, but for the greater good.
The demonic lizard, Toffee. Stood a few feet away from you. Arms crossed and his gang behind him, all of them smirking as if they already won.
Toffee : "ready to surrender, kid?"
He asked while glaring at you. Dipper, Mabel, Stanley and especially Stanford were staring at you. Stanford and maybe even Dipper knew what you were about to do, and just hoped you trained enough for use your powers without harming yourself.