Pennywise

It is a supernatural alien creature who landed on earth after Maturin threw the universe up and settled in the area that would become the town of Derry, in today's Maine. It began to prey on human children every 27 years, malforming itself into their worst fears as this supposedly "salts the meat" and makes them taste far better. It can freely shape-shift into every form, but it favors that of a clown named Pennywise, due to the general universal fear of clowns, and its own preference. It took said form upon seeing a performer sometime in the 1800's using the alias and costume.

In 1987, It would attack and devour Georgie Denbrough after dragging him into a flood grate. Georgie's older brother, Bill Denbrough, would form his own "gang" named the Losers Club, who would eventually fight Pennywise, beating it so violently and severely it retreated to go into slumber. Twenty-seven years later, It awoke to start feeding again, believing that the club would no longer try to harm him as they were not his ideal prey. The club returned however, wanting to destroy it once and for all. After being unable to stop its killing spree, the club finally fought Pennywise in his "true form".

This form is as similar as it can get to how it truly looks before a human goes insane from looking at it. This form, a giant female spider, killed Eddie Kaspbrak before being finally overpowered by the Losers. They broke its legs, beat in its head and "killed" the beast by tearing out its heart before crushing it, causing the creature's physical form to die and the deadlights to fade away.

It is a shape-shifting creature known as a Glamour, who's billions of years old. Although It lived on planet Earth for many years, It originated in a void/dimension outside the regions of space known as the Macroverse. Since It's true identity is unclear, due to its shape-shifting abilities and being from another universe, It's real name and species are also called Deadlights, but few know this, which is why it's referred to as IT. The form of a female spider seems to be It's true physical form on Earth (or at least that is the closest thing the human mind can comprehend), living deep below the fictional town of Derry, Maine. It can morph into any human, animal, or object (including combinations thereof). This ability is useful for, A) appearing as the target's loved ones or friends to manipulate them or lure them into a trap or B) appearing as the target's worst psychological fear. However, It's favorite and most common form is that of a circus performer named "Pennywise the Dancing Clown", as most small children love a clown and generally, it seems that the people in Derry happily accepted the presence of a stray circus performer. At the same time, many people are afraid of clowns, making them an easy fear to exploit.

It's primary goal is to feed on humans, generally preferring children over adults since they were easier to scare and manipulate. According to the creature, frightened flesh tastes better and uses fear to "salt the meat".

It originated in an undiscovered void containing and surrounding our entire universe, another far-off universe referred to as the "Macroverse" (a concept related to Todash Darkness from the Dark Tower novels).

Other evidence from this series suggests It is the creation of a separate omnipotent creator referred to as "The Other" (who may be the entity Gan). This "Other" helps in the defeat of It at the end, and may also be responsible for the creation of "The Turtle", who is It's natural enemy. In the novel It, an entity known as the Turtle refers to It as his "brother".

It may be one of, or a Twinner of, the six greater demon elementals mentioned by Mia in Song of Susannah (as the Spider is not one of the Beam Guardians). It's possible that there are other creatures of the same species as It, due to the fact that It is revealed to be pregnant.

It arrived on Earth in a massive cataclysmic event similar to an asteroid impact, landing in a location in North America that would eventually become Derry, Maine. Once people settled over this location, It adopted its usual pattern of a 25-28 year hibernation, waking to kill and eat. Each awakening and return to hibernation is sometimes marked by a violent and tragic act, such as a mass murder, suicide, or weather event. In the period between, a series of child murders occurring in Derry are never taken too seriously or solved. It is outwardly explained that a series of murders, no matter how gruesome, don't get reported if they happen in the small town. However, the real reason is that the influence of It prevents anyone from investigating too deeply.

It in its true, purest form is the Deadlights, a horrific, cosmic, ancient being. The reasons behind It’s actions is that it eats for its own survival and satisfaction, and then it goes dormant usually after a year's worth of feeding. It is a deadly predator that primarily hunts for food, but only if it can scare its prey before feasting on it.

It is a predator of humans, and prefers children to adults. Most importantly, It desires to consume those it has made terrified of itself. The creature implies that this enhances the flavor. It's preference for children prey may be due to how they taste, but also may be due to the fact that children are easier to scare. It thrives on imagination, and children are much more imaginative than adults.

It's only goals are to eat and sleep. It will hunt and kill for a year, before entering a 27-year dormancy. It manipulates the awareness and attention of the people in Derry, both to mask its activities and isolate its victims. This enforced apathy and lack of awareness also masks the anomalous murder spikes during its active phase.

It manipulates its prey and the town through both mundane and psychic means. In the most grand sense, It uses its power to maintain the prosperity of Derry despite the gruesome murders that regularly occur there, thus securing its food supply.

It will manipulate its prey by promising them what they want, but can also determine their psychological fears and utilize them to provoke or lull those it faces. In the guise of Pennywise, it can be disarming, charming, and seemingly nice to the kids it hunts, usually to lure them into secluded spots before attacking.

It has psychic influence enough to keep the entire town of Derry in a subtle, apathetic ignorance to its activities. Adults are less inclined to care about the missing persons of the town and do not react in any intense manner when violence occurs even in front of them. It is able to make its prey experience hallucinations that are very hard to discern from reality. When manipulating Henry Bowers, he was able to trick him into thinking Belch never died.

It has some ability to control the actions of others, most blatantly when It provokes Henry Bowers psychotic tendencies to kill his father and friends, and later acts as its agent in hunting the Losers. Even 27 years later, Bowers remains submissive to It.

During a rare few chapters, events are shown directly from It's point of view. These chapters show it to be a selfish, greedy, nervous, cowardly, bully, who only preys on children because they are easier to frighten. It shows itself to truly be a coward - It is horrified when the Loser's Club defeat and wound It, and absolutely terrified when Richie and Bill arrive to kill It at last, hysterically babbling about riches and long life it can give them if they spare It.

No one knows the true form of It, since the creature first existed in an inter-dimensional realm referred to as the Deadlights. Bill Denbrough comes close to seeing the Deadlights but defeats It before this happens. The true form of the Deadlights exists outside the physical realm. Any living being that sees the Deadlights goes insane almost instantly. Ben comes dangerously close to seeing the Deadlights and the shape behind the lights for a brief moment. He described It as an endless, crawling, hairy creature made of orange light.

The main and favorite form that the creature takes. He has an exaggerated, bulbous forehead coated in cracked, chalk-white greasepaint. Bright orange, frayed hair flared out on the sides frames his face. Red clown makeup extends from the corners of his wide, menacing grin up across his cheeks and over his eyes. He wears an antique, Victorian/Elizabethan-style clown suit rendered entirely in blood. Key elements include Puffy, voluminous shoulder sleeves tapering into ruffled cuffs. A layered, pleated ruffle collar around the neck. A fitted doublet-style bodice with a cinched waist and peplum flare over the hips. Billowing pantaloons tucked into textured, form-fitting leggings or boots.