Random thoughts on the topic:
- the Chinese supposedly used gas in bamboo pipes for cooking and stuff... meaning that here, there could be areas with a relatively high standard of living, representing the civilization. The rest of the world would be more or less unstable wilderness. City states and roaming tribes. Also, steam tech will be used.
- a monster that likes to camouflage and push or drive unsuspecting victims into the warmer waters. Likes the dinner properly cooked.
- important skills: smell in general (many types of gases, some of them are poisonous or indicate danger) and by extension taste (poisoned food is easy to get here); and tremor sense (knowing when a geyser erupts or worse). May be honed by the people, or they could have animals for it.
Really depends on how advanced you want to have the place, whether you'll have magic, etc. But there.