You gave a very good spin to the genre with the weapon/surroundings interactions, you should definitely flesh things out even further by generating more complex biomes, changing the way the enemies behave depending on the terrain, so that you can retreat to more favourable ones against certain encounters, and most importantly improving weapons mechanics. The threat level system you use is fine for enemies, but it makes it very clunky to use weapons to, say, break stone. I think it would be beneficial if weapons displayed a list of tiles they can break, and had a separate, fixed usage rate with which they break them.