Multi-Bear is a large magical beast whom Dipper went to conquer in order to attain manliness. It has eight heads, with one main, intelligent head, capable of human speech. It lives in the Multi-Bear's cave at the top of a high mountain.
Background
Physical appearance
The creature has one large bear head with nine smaller heads, and has multiple arms, sharp claws and dark brown fur, all the bears have black noses and yellow eyes. Each head is sentient, but the smaller ones have animal intelligence. On the bear's back, a second partially-formed body sticks out housing one of the heads. During Weirdmageddon, some of the heads gain an eye patch.
Personality
Though he seems ferocious to Dipper at first, he soon realizes that the Mutli-Bear is actually a rather nice guy. The Manotaurs declared him their enemy because he engages in some activities not considered "manly", such as listening to BABBA.
Role in the series
Dipper was sent by the Manotaurs to conquer the Multi-Bear, and bring back its head (or one of them). The Multi-Bear was very ferocious and threatened to kill Dipper if he did not leave his cave. Dipper refused and he and the bear began fighting. Dipper ultimately won and was going to conquer the Multi-Bear. The Multi-Bear had one last request: to die listening to his favorite song, Disco Girl. Dipper realized that he and the Multi-Bear had something in common, and decided not to slay him.
The Multi-Bear is one of the creatures who sides with the rebels during Weirdmageddon. He helps pilot the Shacktron with the others while fighting Bill Cipher and his minions. After the crisis subsides and Bill is defeated, the Multi-Bear is seen among other Gravity Falls creatures waving off Dipper and Mabel as they return home.