"And then it spiraled."

 In my novels, it is not unknown for me to use an idea at the tail end of a novel, and decide that “You know, I could build an entire novel around this idea.”For example, at the end of Infernal Affairs, the ultimate villain was a warlock, and he used living shadows for a weapon.It occurred to me that I could build an entire book where living shadows are a threat. What if they were slowly