The natives are Bronze Age, roughly similar to West Africans on Earth. There is going to be an element of magic in this game (wasn't planning on it, but that seems to be popular demand, so I'll work it in) but not a wizard's tower on every street-corner. Magic is relatively uncommon, and feared in many quarters. The native society is nominally matriarchal (we're not talking militant Amazons here, but overall most leaders just tend to be female). The culture is agrarian, and largely peaceful, existing on about thirty square miles of land between the foothills and mountains, and the ocean.
The ocean is relatively unexplored. The mountains...well, those are viewed with fear, and legends of hungry, large beasts and strange, savage races beyond dominate the tribe's folklore.
A few years ago, a new, strange tribe appeared, flying a banner unseen before:
They carried weapons of a sort the tribe had never seen before, loud weapons that could put a piece of metal in a target from afar. Opinion was divided on whether or not they were amongst the dreaded inland tribes beyond the mountains. No one knew for sure. They didn't seem bent on conquest...but they did see the tribe's women as up for grabs.