Accordingly, the gang force Pennywise to become small and weak, after which they're able to remove his still-beating heart and crush it in their hands, finally ending his reign of terror.
Literature. In the novel, It is a shapeshifting monster who usually takes the form of Pennywise the Dancing Clown, originating in a void containing and surrounding the Universe—a place referred to in the novel as the "Macroverse".
In the novel, IT never experienced emotion until IT encountered the Losers Club, in which IT learned fear and hatred first hand, something that was completely new to IT.
Image via Warner Bros. Finally, Pennywise is beaten into submission. He scurries away, utters the word "fear," and partially disintegrates before falling into the void. It's a powerful defeat of a powerful monster, and it's satisfaction enough were IT to remain a single film.
“Pennywise the Clown” was never human. He doesn't have a “backstory” in that sense. He was never anything other than what he is in the book.
In both the book and the films, It is an ancient alien creature, older than civilization, and in King's novel, older than our universe. It feasts on the flesh of humans simply because our fears are easy to manifest and they make us taste better.
He took the form of a clown most frequently, Mr. Bob Gray or Pennywise, but his true form is an ancient eldritch entity from another universe who landed in the town that would become Derry by way of an asteroid and first awoke in 1715.
This proves to be its undoing; Eddie nearly chokes it when it takes the form of a leper and is small enough for him to do that. When sufficiently weakened, the Losers kill It by crushing the heart it must have in the form of Pennywise the Dancing Clown.
It's weaknesses are courage and heart. For the sake of spoilers, I won't go too much into the Ritual of Chüd, but suffice it to say that if you want to defeat It, you've got to have the two traits listed above.
Stephen King's 'IT' introduced readers to a one-of-a-kind creature that can take any form, the most common one being Pennywise the Dancing Clown, and as menacing as it is, this creature has one big enemy it's truly scared of: Maturin, the turtle.
This is one of the most interesting Hollywood couplings we learned about in quite some time. Apparently, Pennywise and the Babadook are dating. In fact, they're in a long term committed relationship.
Martin Morgan Pennwise is (biologically) asexual and has the ability to reproduce. Therefore even though King describes pennywise as a female further into the book, 'IT' is (technically) neither male nor female.
A god of destruction, not just of our world, but of multiple worlds and even multiple universes. It originated in a vast cosmic void between worlds that has been called, at times, the Macroverse, and in King's Dark Tower series, the Todash Darkness, in a space It refers to only as the Deadlights.
Kersh is Pennywise's daughter.
As well as having his right arm bitten off, Georgie is trying to crawl away but he was dragged into the sewers and devoured by Pennywise, with an unnamed older woman and her cat being the sole witnesses of the horrific scene, including before Georgie lost his arm.
The turtle is a force of benevolence and is guided by compassion, whereas IT represents chaos, evil, and fear. They are diametrically opposed. Because they are both interdimensional entities with equal powers, the turtle could kill IT if it wanted to, therefore it's understandable that IT is terrified of it.
In their final battle, the Losers' Club was able to kill Pennywise by reducing him to a child-like form as they overcame their fears.
IT thrives on chaos; an exact 27-year pattern is way too predictable for a being of pure evil. Rather, IT wakes up roughly every three decades, and stays away for a different period of time.
So basically, in the book, Bill heeds the advice of the gigantic, wise turtle god, completes the Ritual of Chüd, and defeats It using the tongue twister that's meant to help his stutter: "He thrusts his fists against the post, but still insists he sees the ghost." And don't even get us started on what happens the ...
The spider-clown shrinks as the Losers hurl taunts at It, until it's tiny and weak enough that they pluck out its heart and squash it into nothingness. In the end, they defeat Pennywise by, uh, making him feel really bad about himself.
Pennywise's origins are briefly explored in both the book and It: Chapter Two, where it's revealed that he is a being that crash-landed on Earth from another dimension hundreds of years ago.
Throughout the summer and their trials against Pennywise and the school bullies, the Losers realize that none of the adults in Derry can actually see Pennywise or the horrors he is committing against the children of Derry.
The concept of clowns has been traced back to the Fifth Dynasty of Egypt, but the modern circus clown developed in the 19th century, so by the time King's novel is set (the first part of it), Pennywise was around 200 years old.