Episode 4 of It: Welcome to Derry, titled “The Great Swirling Apparatus of Our Planet’s Function,” explains the origin of Pennywise. After Dick Hallorann approaches Taniel to know the whereabouts of Pennywise, the show presents a flashback revealing the origins.

What does It: Welcome to Derry Episode 4 reveal about Pennywise?
Hallorann uses his psychic abilities on Taniel to look for It. After the painful inspection, the native American kid decides to share the legend of “the monster in the Western Wood” from his childhood.
Taniel revealed that Pennywise came to Earth from outer space. “Millions of years ago, before the time of the first people, an evil spirit was cast down from the darkest part of the night sky, bound inside a falling star,” Taniel began.
After it came crashing down, the star broke open and released the evil spirit. “It roamed the woods for many snows and countless moons, until the creation of our first ancestors,” Taniel added.
It became known as Galloo among the indigenous tribes and began its reign of terror. However, the tribes protected themselves with weapons made from the fallen star. The Natives managed to keep the evil contained in an invisible boundary.
But the arrival of the settlers changed everything. Despite warnings from the Natives, the Europeans hunted in It’s territory. This led to Pennywise escaping from the prison and growing stronger.
Taniel then revealed that 13 sacred pieces from the star were buried around the Western Wood to create pillars for containing Pennywise. “Our people made a sacred promise to guard the pillars and keep their places secret, so the monster trapped inside could never break free,” concluded Taniel.
Following the flashback, adult Taniel says, “Follow the tunnels under the old well and you’ll find the pillars.” The show then reveals the familiar Neibolt House, also known as the Well House, where Pennywise lives.
