A/N: Welcome! I do not own Gravity Falls (unfortunately), or any other accidental references I might've made. I do not claim to have made up this prompt.

Mabel giggled in anticipation, chewing her bottom lip as she typed in the password to her laptop. Her friends, Candy, Grenda, and Pacifica huddled around the screen behind her, waiting to see the results. Pacifica rolled her eyes.

"Mabel, this is stupid. You're only gonna turn eighteen once, why waste it on 'summoning a demon'? I mean, who died and made you your brother?" The blonde spat, flicking a lock of thick flaxen hair behind her shoulder with well-manicured nails. Mabel turned to her best friend and frowned. Mabel knew that when it came to her opinion, Pacifica didn't have a filter. As soon as some snarky remark came to her mind, it was past her glossy lips in two seconds flat. Mabel had learned to accept that over time, but it still didn't make it any less obnoxious.

"Come on, Pacifica! It's not like it's actually going to work. Plus, maybe the demon can get you those extensions you've been wanting!" Mabel grinned, poking Pacifica in the cheek. The slightly older girl merely scowled in response as the others giggled with each other. Out of the corner of her eyes, Mabel noticed the screen on her laptop had switched to the Google search bar, signaling it was ready for her to type in her request. She bit her lip again and readied her fingers at the keyboard.

How to summon a demon, she typed, jamming her thumb on the [enter] key. An abundance of search results came up, and Candy leaned over and clicked on the first one, .

"The first one is usually the one you're looking for," Candy added, tucking a lock of black hair behind her ear. The girls turned their attention back to the screen.

"There are many reasons why one would want to summon a demon...blah blah blah, introduction, yada yada….Oh! here we go. 'The first step to summoning a demon is to draw a circle of 24 inches on the ground or floor. Use whatever substance is available to you.' Er...I have Wite-Out…?" Mabel looked around the room for consent, and after getting it, returned with a bottle of Wite-Out in hand. As per the rest of the instructions, Mabel pricked her finger and chanted, "Triangulum, entangulum. Veneforis dominus ventium. Veneforis venetisarium!" All the while trying not to laugh as her friends playfully teased her in the background. After completing the ritual, a moment of silence passed as everyone waited with bated breath, then Mabel let out a shaky, relieved sigh.

"Phew! For a second there, I actually thought something was going to show up!" She declared laughingly, facing her friends.

"I know, I'm relieved too!" Came a grinning, nasally voice from over her shoulder. There was another pregnant pause before Mabel screamed and turned around, falling backwards on her rear.

She looked at the tall man. He dwarfed her, he was probably 6'2" to her 5'3". His skin was lightly tan and he had wild, golden hair. A black eyepatch covered his right eye and the one eye that was showing held a malicious glint and was framed by dark, rather long lashes. He was leaning his forearms on a cane, grinning with mirth. He was rather enticing to Mabel, not that she would ever admit this to herself.

"Ohmygodohmygodohmygod y-y-you WEREN'T ACTUALLY SUPPOSED TO SHOW UP!" She shrieked. Her friends watched in absolute astonishment and horror as the demon cackled. "The name's Bill Cipher!" he exclaimed happily. A blue glow surrounded his lean frame before he crooked a finger under Mabel's chin and leaned his face into her ear.

"Guess what? You're bonded with me now," he whispered, grinning like the Cheshire.

A/N: thanks for taking the time to read the first chapter of Bonded! I really appreciate it!