Seven years too late I've realised I missed a wonderful opening lines for one of the NPCs - the banking and insurance magnate known as The Crimson Claw, who has grown so big that he dwarfs any player character and can never leave his vaults - the tunnels are too small for him.
"I like the smell of debtors in the morning... they smell like... breakfast..."
I could almost kick myself that I didn't put that in, but I think it's really a bit late now. And to be honest, while it feels like a fun line, it might not quite cause the sensation of mind-numbing terror I want characters to feel if they meet him.