Books and movies exist in the same "omniverse" that is made by a single Author - Stephen King, so there are no contradictions and copyright issues here.
Cool. Pennywise/Deadlights can exist outside of the Tower, as well as Gan, The Crimson King, The Crimson King's family (a bunch of Todash Space Monsters).
There is no reason to scale Pennywise/Deadlights beyond Gan and the Crimson King.
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Gan and The Crimson King are the only big players who can manipulate fate and authors in this verse:
The Dark Tower states that what we call fiction actually exists out there somewhere in reality in some form. Authors, artists, etc imaginations touch on these other worlds and they write/draw/whatever these things they see. However they don't create these worlds, Gan does:
The Crimson King/Dis can also do the same:
A little info on how changing reality via the story works:
Another example, when the author makes the leap from the "real world" and arrives in the fictional one:
Sometimes Stephen King will leave Deus Ex Machina's for characters directly:
An example of an artist changing reality through artistic talent - erasing a cancerous sore:
In Duma Key, a child able to change reality with her drawings attracts an ancient entity:
The entity known as Perse also encounters an adult with the same ability, an ability that was accidentally used to kill Candy and also used to fix Wireman's eye:
There's also a King short story where a boy makes his uncle a super advanced computer, which warps reality and time.
And the Macroverse is not beyond the Tower.
The Dark Tower Glossary:
The Tower > The Macroverse.
Eroding the Beams would lead to the Dark Tower collapsing, and all reality, the macroverse, would cease to exist. The Guardians guard and support all the Beams of the Dark Tower, which means they support all the universes of the macroverse, which are contained within the Dark Tower. The macroverse as described in the Gunslinger is a place where an entire infinite universe is less than an atom in a universe on a higher level, up and down forever.
Gan made creation, and locked the Crimson King out of it. This is the reason for his obsession in destroying the Tower:
It is not hard to enter the Todash Space, that exists "beyond the Macroverse":
Maturin is just a "little god":
Gan or the Red King > Author > Maturin and Pennywise/Deadlights, who are bound to their storyline.
The fact that they replaced magical Beams with technology shows the same level of power:
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Long story short: The Final Other = Gan >= The Crimson King > The Dark Tower > Old Ones, the Imperium > the Demon Elementals and the Guardians (including Maturin and IT/Pennywise/Deadlights)