The Menace is the main antagonist in the first 12 books of the first story arc in the series Goosebumps: Horrorland by R .L. Stine.
In books 1 through 12 of Goosebumps: Horrorland, kids get invited to Horrorland. Horrorland is a park where the horror is real. Horrorland is run by monsters called Horrors. Throughout the series, the kids run away from the Horrors and have scary adventures. The only Horror that they think that they can trust is Byron. Byron tells them to escape Horrorland and go to Panic Park where they will be safe. When they make it to Panic Park, they realize that Byron was working for The Menace.
Panic Park is full of people that turned into shadow people after the previous park went to a different dimension. Everything in Panic Park is gray.
In the book Escape From Horrorland, the kids meet The Menace for the first time. In the book The Streets of Panic Park, The Menace reveals his plan and he also reveals that his face has two sides. His plan is to scare the kids enough to make a meter reach the top. Once the meter reaches the top, Panic Park would be back to normal. The problem is, the kids might scare themselves to death. The villains of the previous novels doubt their own survival as well. The villains tell the kids that laughter will defeat The Menace. Slappy the Living Dummy defeats The Menace by making all of the kids and villains laugh. The Menace and Panic Park gets destroyed while the kids go back home.