I said Yellowstone, but what I was really thinking of was more like Arenal in Costa Rica. Hot rivers that get into the 110 degree range in spots, natural bath pools, etc. This would be from volcanic activity deep inside the mountain. Not looking for active geysers, acid pools, lack of plant life, etc.
I am afraid you lost me on that. Does that mean I am better off justifying the large mountains with tectonics or volcanic activity?
Honestly, I would love some advice on that. My initial thought was that it would be narrower but deeper near the head and widen somewhat as it slows and gets to the sea? Do these canyons sometimes have large waterfalls at their heads? That makes sense to me, but not sure if it is just wishful thinking.
I would lean more toward the steep walls, but it will likely vary somewhat naturally depending on the material being cut through and the speed of the water at that area, correct? Basically, as long as it is very difficult to traverse terrain that makes you vulnerable to attacks from above it will serve my purposes. Magic will make things a bit more difficult, but those with the ability to move large numbers of troops in this manner will be both rare and targeted.
It will be a contested border between protectorates of two colonial powers in the area. The southern colony has been neglected since the silver and mercury mining has become more difficult (similar to Peru in the 1700's by Spain). The northern colony is more independent and somewhat similar to the US near the time of formation, but pre-Revolution. The rest of the border is either harsh mountain terrain or a very dangerous tropical rainforest on the southwest border. The conflict is more simmering than active at the moment, but that could change depending on the actions of the party(ies) who will be adventuring.
I will post an updated map to my WIP thread tomorrow at some point, my eyes are too tired to try it tonight.
- Ernie