A tip I read a long time ago (and I feel bad for not remembering who originally wrote it) puts forth the following questions and statements to help you create a realistic world. I think it pertained to general sci-fi and making new inventions, but I find it helps for almost anything.
When you decide to add an element to your world, ask yourself the following three questions:
Why?
How?
What Result?
Why was this device created? Why was there a war? Why did people settle here? Whatever the situation, you need a believable reason why it happened. Then you have to ask yourself how it happened, and explain it in a way that's consistent with your world. How was the device created? Using what resources? How was the war fought? Who were allied with the main combatants? How did settlers arrive here and build their settlements? What local resource did they use to build their homes that makes them different from other areas? Then think of the results. What was the device used for? Who won the war and how many died on both sides? What happened to the new settlement?
Once you have it in your head why and how things happened and you know the results, remember the two facts below:
Never in the history of the world has any society been perfectly unanimous in its’ response to an event.
Nor has any innovation been introduced into the world without unpredictable side effects.
These add the real believability. Who thought the device was the work of the devil and wanted to outlaw/destroy it? Who protested against the war and perhaps aided the enemy? Who refused to settle in this place and either moved on or returned home? Answering these questions gives you realistic opposing groups and ideas, possibly even new strange devices designed to counteract the ones you originally thought of as the real innovation. This adds layers of complexity and realism, or at least it seems to work for me.