So I read this at a description. Have to say, as a setting I love it and I absolutely would love to play the game.
Here is a trap though, you have a brilliant setting, but setting is the easy part. How will this become a story, where is the twist? If you don't plan ahead for this a little bit then there is a risk that the story just runs out of ideas and peters out once you reach the war.
So what could happen? You have a lot to work with ...
- Maybe we can discover a cure for our sister, derived from some? But what risks would you take to actually take to acquire it? Would you risk your own life? The survival of your unit? Would you risk losing the war?
- Perhaps we can discover avoid the draft and join rebels instead that are allied with a faction among the monsters?
- Perhaps we can discover that the war is a scam to control the population, and the monsters aren't that bad after all?
- Maybe we can find a treasure, but then we would make sure that we keep it somehow?
So basically what I am doing here is going through every sentence of your setting and thinking how could the story change this.