Sewer Monster has never seen the sun.

"I've never seen the sun. I've never let its honeyed light warm my pale flesh. I've never felt the wind, either. Real wind, not the hot, putrid wind generated by miles of sewer. I've also never walked barefoot through the grass, or laid down in a field to let my imagination mold clouds into the shapes of familiar things...The only time I've been above ground was on a cold, moonless night many years ago. A young woman saw me, screamed, and fled in terror. It upset and confused me so much that I haven't been back up since. Of course, this was before I realized my mouth looked like some sort of hellish asshole."