It

It, also known as The Deadlights, is a malevolent ancient cosmic being.

It was the creature that terrorised the town of Derry, Maine for hundreds of years. It was one of the countless beings spawned into existence at the dawn of creation by "The Other" (known to mortals as The Big Bang).

Origin
Its' true form, and all of the other Deadlights, sprang into existence by a presence known as "The Other". Like many of the Deadlights, It was born malevolent, wishing to feast on the fear of other beings. It chose one planet, Earth, 'knowing' that one day the planet would give rise to one race of beings who would be able to satiate its appetite.

Landing in Derry, Maine
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 the town of Derry, Maine millions of years later. Once human beings settled in the area, It began its pattern of a 27 year hibernation, waking to terrorise, kill and eat the towns 'tastiest' residents. Each awakening and return to hibernation is sometimes marked by a violent and tragic act, such as a mass murder, suicide or a disastrous weather event. Over the centuries, Its influence grew even stronger over the town, preventing any residents, namely the adults from investigating or reporting the murders or strange occurrences too deeply, allowing Pennywise to continue its cycle.

1984-1985
In 1984, Pennywise awakened once again. One night, a young couple, Adrian Mellon and Don Hagarty were set upon by three homophobic teens, Chris Unwin, Webby Garton and Steven Dubay, who proceed to assault the couple and throw Adrian off of a bridge. Pennywise, newly awakened drags a half living Adrian out of the river, and bites into his side while Don and Chris look on. Adrian's death is reported, but Pennywise's existed is dismissed.

Return to Life
Though the Losers' Club succeeded in defeating Pennywise once and for all, It was far from defeated. With the surviving members of the Losers losing all memory of their home town and the nightmares they endured, It was free to rain terror on the town once again. But with Pennywise and its 27 years feeding cycles null in void, It would find a new way to sustain itself.

Known forms

 * Pennywise the Dancing Clown: It's most prominent form on Earth, having used it to draw in it's main prey, the children of Derry, Maine.
 * As Pennywise, the creature has taken on the form of countless other creatures and beings
 * True Form: It, as a being born outside of time and space, has no true form.
 * To the surviving Losers Club members in 1985, they perceived a 'true form' of the creature, related to it being a creature of consumption, evil and disgust. They envisioned the creature as a giant spider-like creature, with multiple arms, and a disgusting smell.