Who is the main villain in the 2017 horror film "It"?

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.

King stated in a 2013 interview that he came up with the idea for Pennywise after asking himself what scared children "more than anything else in the world", and feeling that the answer was clowns. King thought of a troll like the one in the children's tale "Three Billy Goats Gruff", who inhabited a sewer system.

The character was portrayed in its Pennywise form by Tim Curry in the 1990 television adaptation, in the 1998 television adaptation by Lilliput, and by Bill Skarsgård in the 2017 film adaptation and its 2019 sequel "It Chapter Two".