Hopefully chapter 2 will explain how they manage to beat it. Like in a Lovecraft story, you get another entity involved. In the book, this entity (the turtle I believe) told them specifically what ritual to perform (CHUD I think). Otherwise the true form is those intangible dead lights. So it wasn’t the just the power of friendship or sewer orgy/train. Also, one of Its’ offspring or relatives is in the Dark Tower, though he prefers to make people laugh themselves to death.