Morrison: Yeah, it's a bit of that. It's also the idea that they're like angels as well. For me, the cool, essential idea of all stories being real creates this great cosmology to play with. It's the notion that the white page itself is a void, and in the context of the DC Universe, well that's God or The Source. In the white page, or the void, anything can happen, everything is possible. As I dug down closer to the very root of the activity I find myself engaged in as a career, I was thinking "what is the basis of the comic book story? What actually is it?"
In the case of comic book stories, it's the war between white page and ink. And who's to say that the page might want that particular story drawn on it? [laughs] What happens if the page is a bit pissed off at the story that's drawn on it? So I thought of the page as God. The idea being that the Overvoid – as we called it in Final Crisis - of the white page as a space is sort of God. And it's condensing stories out of itself because it finds inside its own gigantic white space, self-absorbed pristine consciousness, it finds this little stain or mark, this DC Multiverse somebody has 'drawn'. And it starts investigating, and it's just shocked with what it sees, with all the crazy activity and signifying going on in there. It then tries to protect itself from the seething contact with 'story' and imagines a race of beings, 'angels' or 'monitors' (another word for angel, of course) to function as an interface between its own giant eternal magnificence and this tiny, weird crawling anthill of life and significance that is the DC Multiverse.
This is from Grant Morrison's IGN page on the Overvoid.