- I'LL KILL YOU ALL! Ha ha ha! I'll drive ya crazy, and I'll kill you all! I'm every nightmare you've ever had, I am your worst dream come true. I'm everything you ever were afraid of! ARGH!!!
- - Pennywise to the Losers' Club
It (sometimes capitalized as IT), more commonly known as Pennywise the Dancing Clown, was the titular antagonist of the Stephen King novel and film of the same name. He was a demonic entity who would almost always disguise himself as a clown to attract children so he can capture and kill them, as he finds that their fear is most purest and most delicious kind of fear of all. He is the devil in opposition to the benevolent creator known as the The Turtle and both are creations of The Other.
It is part of the disasters that occur every 30 years in the Maine town of Derry.
Unlike many horror monsters before him, Pennywise the Dancing Clown isn't against killing children; in fact, he actually prefers to kill children as they are an easier target. This is probably why he chooses the form of a clown, a figure that both entertains and terrifies many young children. It has razor sharp teeth that he can use to kill people.
As the film progressed, a group of children known as the Lucky Seven (also mockingly referred to as the "Losers' Club") forms together to kill Pennywise and end his murderous reign (after he had killed the brother of one of them) and apparently succeed after tracking him down to his lair. However, Pennywise, being a lesser-aspect of a higher being, isn't going to stay dead forever and he swears revenge on the gang for his defeat before he vanishes into nothingness.
Many years later, Pennywise keeps his promise and comes after members of the gang, who are all adults in the present day, to kill them. This prompts the gang to reform and battle Pennywise again in order to kill him yet again and save themselves from his wrath. At the end of the film, the gang does manage to defeat Pennywise again, but in that final battle, he takes the form of a spider-like monster (which is revealed to be his true form) rather than the clown disguise (which he uses for most of the film). He is killed when Bill pulls out his heart.
The film lacks many elements of It that the novel includes. In the novel, It is an eternal entity that is almost as old as time itself. It is the natural enemy of Maturin (The Turtle), who both exist in the Macroverse.
After arriving to Earth, It would sleep for approximently 28 to 30 years at a time, then awaken to wreak chaos and feed (primarily on the fear of children). It is able to take many more forms then the film depicts, including werewolves, bats, leeches, and even Jaws. Anything a child is afraid of, It could become.
Also in the novel, It is only able to be stopped when Bill performs the Ritual of Chüd.
It apparently originated in a void containing and surrounding the Universe, a place referred to in the novel as the "Macroverse" (a concept similar to the later established Todash Darkness of the Dark Tower Novels). Its real name (if, indeed, It has one) is unknown—although at several points in the novel, It claims its true name to be Robert Gray—and is christened It by the group of children who later confront it. Throughout the book, It is generally referred to as male; however, late in the book, the protagonists come to believe that It may possibly be female (due to Its manifestation as a large female spider). Despite this, Its true form is never truly comprehended. Its final physical body is that of an enormous spider; this is, however, the closest the human mind can get to approximating its actual form. Its natural form exists in a realm beyond the physical, which It calls the "deadlights". Bill Denbrough comes dangerously close to seeing the deadlights, but successfully defeats It before this happens. As such, the deadlights are never seen, and Its true form outside the physical realm is never revealed, only described as writhing, destroying orange lights. Coming face to face with the deadlights drives any living being instantly insane (a common H. P. Lovecraft device). The only known person to face the deadlights and survive is Bill's wife Audra Phillips.
It's natural enemy is the "Turtle," another ancient Macroverse dweller who, eons ago, created our Universe and possibly others. The Turtle shows up again in King's series The Dark Tower. The book suggests that It, along with the Turtle, are themselves creations of a separate, omnipotent creator referred to as "The Other". The Turtle and It are eternal enemies (creation versus consumption). It may in fact be either a twinner of or the actual one of the six greater demon elementals mentioned by Mia in Song of Susannah, as the Spider is not one of the Beam Guardians. It arrived in our world in a massive, cataclysmic event similar to an asteroid impact, in the place that would, in time, become Derry, Maine.
Throughout the novel It, some events are described through Its point of view, through which It describes himself as the "superior" being, with the Turtle as someone "close to his superiority" and humans as mere "toys". It describes that it prefers to kill and devour children, not by nature, rather because children's fears are easier to interpret in a physical form and thus children are easier to fill with terror, which It says is akin to marinating the meat. It is continually surprised by the children's victories over It and near the end, it begins to question if It is not as superior as It had once thought. However, It never believes that the individual children are strong enough to defeat It, only through "the Other" working through them as a group.