The horror, the horror.
Having decided that horror was the puzzle I wanted to answer with this particular game the important question was one of setting. To be honest it wasn't a very difficult question to answer. I knew I wanted the game to be resilient to expansion which ruled out single story settings such as distant mountains or subterranean caves. That led me to one of two settings. The most obvious is the isolated mansion, the classic haunted house setup, but I didn't see much point doing what Betrayal at House on the Hill has already done as well as I could imagine doing it. The second setting of a range of classic horror and high tension films was the sci-fi, isolated space ship/station. While there have been single setting, single story sci-fi set games I genuinely don't think an attempt has been made to create a single setting, multi story sci-fi horror game. Which is odd when you think about it since it saves needing to explain why you can't just walk out or call for help and is rich with iconography and excellent horror survival stories. Just as a quick list, 2001, Alien(s), Sunshine, The Thing and Event Horizon in cinemas, System Shock and Dead Space in computer games, and a range of TV shows from X-Files and Dr Who to Star Trek. For that matter, imagine how genuinely terrifying tribbles could be if they weren't so cute.
So I had my basic task set for me, as a set of rules, setting and characters to allow for a range of stories and as much expansion as possible. As such things seemed pretty clear, a modular board, usefully generic characters and a set of mechanics that both provide interesting pressure as stand-alones but have the flexibility to describe a multitude of situations.