The Deadlights are the true essence behind Pennywise, a malevolent force far deadlier than what both the characters and audience initially perceive. They add layers to the monster’s villainy, making the clown façade even more terrifying than portrayed in the films and the “It: Welcome to Derry” series.

Delving into Pennywise’s past reveals that the Deadlights aren’t just a tool used by the creature; they are its very essence. These energies grant It the supernatural abilities it possesses, allowing the creature to wreak havoc in Derry in otherworldly ways.

In its purest form, It is nothing but the Deadlights—a primordial, extradimensional entity that has been marooned on Earth for ages. It chose Derry as its hunting ground, emerging every few decades to feast on the fear of children and spread chaos. Despite its menacing clown appearance, the true horror lies in the Deadlights, which defy the laws of physics and transcend the typical horror villain archetype.

Characters across Muschietti’s “It” films and “It: Welcome to Derry” experience the horrific consequences of encountering the Deadlights. This phenomenon might appear as a form of supernatural hypnosis, but in truth, its effects are far more insidious and devastating than they first seem.

When stripped of all its disguises, It is entirely comprised of the Deadlights. It’s an ancient, extradimensional cosmic horror that was stranded on Earth a long time ago. Here, It made the region that became Derry its domain, and has settled into a groove of periodical year-long reigns of terror where it feasts on fearful children and causes great calamity. However, everything the monster does in the guise of a Derry horror villain is ultimately just an aspect. As the Deadlights, it exists utterly outside conventional physics, which makes It a far stranger thing than just a creepy clown that stalks children. 

As several characters in Andy Muschietti’s two “It” movies and “It: Welcome to Derry” find out to their considerable disadvantage, having Pennywise unleash the Deadlights is very bad news. Visually speaking, their effect can come across as a supernatural hypnosis of sorts, but in reality, it’s something more … and much, much worse.

Because of the aforementioned cosmic horror nature of the Deadlights, a mere human being simply can’t withstand the sight of this true form of the villain. As such, whenever It whips out the lights, it isn’t as much a mind control method as it is a mind destroyer method. Since human victims are utterly unequipped to view them, even the smallest glimpse of the Deadlights is very bad news for the observer. In fact, seeing them is liable to either kill the poor person being subjected to the lights — or utterly wreck their mind. 

Here’s where things get tricky. Though It is stated to be comprised of the Deadlights, not every incarnation of the Deadlights necessarily belongs to It. The Deadlights are stated to be a species of beings, and there are other powerful characters in the Stephen King universe that can wield the Deadlights’ energies in one way or another. 

Notably, the major devil figure in the King universe — the terrifying Crimson King — has access to the Deadlights’ power, and is seen using them to influence events in King’s novel “Insomnia.” The fact that a character as wildly powerful as the Crimson King is happy to use the Deadlights as part of its arsenal is a pretty good indication that the lights are incredibly powerful and desirable tools for evildoers of a sufficient power grade. It also implies that their power isn’t exclusive to It and whatever as-yet unseen creatures might belong in its species.

Since It is a creature that’s far more complicated than it appears, it makes sense that its Deadlights form also has a few surprises in store. Arguably, the biggest is the fact that the Deadlights are connected to a completely different universe, which is known as the Macroverse. 

The Macroverse is effectively a greater universe that serves as the place of origin for at least two incredibly powerful entities in the Stephen King lore. One of them is, of course, It. The other is Pennywise’s arch-enemy Maturin, who’s also alluded to numerous times on “It: Welcome to Derry.” This giant, benevolent turtle-like entity is effectively the Big Good that balances out the evils of It. To give you an idea of Maturin’s — and by proxy, It’s — powers, the gigantic turtle is the creator deity that made our universe in King’s world. What’s more, Maturin did it entirely by accident. (He’s still not the ultimate God of the Stephen King universe, though. That would be Gan, a vastly more powerful figure who plays a major role in “The Dark Tower” books.)

Being associated with the Macroverse and Maturin aren’t the only ways the entire story of “It” fits in the grander scheme of King things. According to some, the Macroverse is actually the Todash Space that fans might also know from “The Dark Tower” series. This would make the Macroverse a vast nothingness with an overabundance of monsters, which might suggest that there are far more entities lurking about the place than its two most famous denizens. 

One thing that the “It” movies and “It: Welcome to Derry” make very clear is that Pennywise is one powerful villain. However, it’s also a villain who tends to target children. Narratively speaking, this might seem to put it in a very specific storybook villain category of supernatural boogeymen who are scary, but who can be defeated with the right amount of pluckiness. This even ends up happening in It’s case, courtesy of the willpower-fueled Ritual of Chüd.

However, there’s some evidence that the power It is tapping into is above and beyond any such character. The most interesting piece of evidence to this effect comes from Stephen King’s 2024 novella “Two Talented Bastids” from the collection “You Like It Darker.” The story states that the Deadlights are such an essential component of everything that exists that the majority of the universe is full of them. Even if It doesn’t have access to all of the Deadlights’ power, this means that they’re still a pretty wild power for any creature to be tapped into.