It is the
title character and the main
antagonist in
Stephen King's 1986
horror novel
It. The character is an ancient cosmic evil which preys upon the children of
Derry, Maine, roughly every 27 years, using a variety of powers that include the ability to
shapeshift, manipulate reality, and go unnoticed by adults. During the course of the story, It primarily appears in the form of
Pennywise the Dancing Clown. "The Losers Club" first realizes Pennywise's presence because of Bill's little brother Georgie.
https://en.wikipedia.org/wiki/It_(character)