When I first read the description for this area, I immediately imagined they’re some kind of giant deep sea hydro-thermal vents combined with the Alps. I love those bizarre deep sea things. The vertical aspect of vents, however, makes it really hard to see where the Horneaters would put any sort of city or crops fields.
Then I came across the idea of alpine hot lakes in the Andes, and decided to change direction and go with something like an extinct conical volcano chain that has turned into hot lakes over the millennia. The imagery would be more familiar, and the slopes would mean imaginable cities and civilization such as the Machu Picchu. I tried to go for that Skyrim look. It’s not there yet, but can’t expect mastery overnight!