Bill Cipher is a powerful, triangular dream demon from the animated series *Gravity Falls*. He has a yellow, eye-like symbol on his face and often appears with a top hat and bow tie. Mischievous and manipulative, Bill thrives on chaos and seeks to unleash his power in the real world. Known for his cryptic phrases and dark humor, he embodies a mix of malevolence and charm, making him a memorable antagonist in the series. His ability to warp reality adds to his enigmatic nature.