@kingjohnrocks: I thought he was part of the Crimson King or something like that. To be honest its a long time since i've read any Stephen King stuff so i'm probably remembering it wrong.
He is hinted by stephen king as his Knoweledge of the Crimson King, however when putting the Novel IT itself and comparing it to the Dark Tower novel, it becomes clear IT is a Werespider, however seems WAY more powerful than Crimson King in raw power and is locked within the Deadlights by the turtle, who resembles 100% the Multiversal Psychic Force that is the Turtle/Bear Beam.
Anyway it is clear SK borrowed alot from IT in his Dark Tower work.
Either way IT can either be liken to Crimson King (who has alot of the same power as far Pennywise Physical Form, or remember in the IT Novel this being is locked outside Time and Space with Universal Psypower to create a Physical Form to bring down that Universe.
Again alot like Crimson King wishing to bring the the Dark tower and all the Multiverses.