The Horrifying Sweaty One-Armed Monstrosity

The Horrifying Sweaty One-Armed Monstrosity is a gigantic one-armed head in Gravity Falls.

History
The Horrifying Sweaty One-Armed Monstrosity came from the Nightmare Realm after Bill Cipher opened the portal. He is a gigantic man's head, with a round nose, a five o'-clock shadow, thick red eyebrows, and red hair on his temples. Attached to the top of his head is a muscular arm which he uses to drag himself. He often asks people to get into his mouth.