We had quite a few questions that were deemed off-topic because they asked about specific subjects relevant to the plot of someone's story, and not to writing in general.
I remember a question about "what could cause a lockdown of a nuclear power plant", a question how linguistics of an alien species could develop, something about choosing a believable motivation for a villain... Our current policy for these is "Help the poor soul out of a pinch, send them in the right direction where they could find the answers, and close the question."
Well, currently there is a site in beta (and doing really well) to answer exactly that family of questions: Worldbuilding. I guess mentioning that in the FAQ (the "topicality" of subjects) and migrating relevant questions there would be the right approach.
Questions about creative writing specific to the world depicted: believable fictional creatures, political systems, advances of science, interactions of specific fictional factors with the real world, and other problems directly related to creation of consistent, believable plot elements within the specific setting of your story belong to Worldbuilding.SE.
While Writers answers generic questions that can be applied to a range of stories across a genre, Worldbuilding gives answers to questions specific to the narrow reality of your story.