There isn't any extensive history for both worlds, but you may experiment with Maerus as see fit.   Maerus is the preceding world of Frantumare. Humans inhabited it and the world was basically dying. The plague and famine are the major problem that struck Maerus and the only kingdom in that world is the Kingdom of Laevenon.   Frantumare has both Humans and Feras, but Feras came first. The major conflict in it is between the Humans and Feras, though interspecies occurred between them. You can experiment around with the interspecies relationships you see fit.