The Three Sisters are mountain peaks (NOT 'peeks' - a typo that slipped by in the opening paragraph of the introduction) chiefly known for the quality of the coffee grown on their slopes and the market that has grown up in the valley below where the three peaks meet to trade in coffee and other produce from the area. Quite sensibly the market operates as a 'free trade zone' outside the influence of all the adjoining kingdoms, a place where making money is all-important and what law there is exists solely to enable trade.
Naturally, this has drawn a few folks who have fallen foul of the law elsewhere, as provided they don't interfere with commerce nobody cares what they might have done back home. These and market officials and a few people catering to the needs of residents and visitors alike, form the permanent community here: others ebb and flow depending what's in season and being sold at the market. One remarkable establishment is the King's Club, formed to provide a refuge for deposed monarchs (although dictators and others who have fallen foul of those they sought to govern are equally welcome). Unsurprisingly, it's a hotbed of intrigue. Quite a few would like to regain the power they once held and plot to that end, others trade in the secrets they learned whilst they were ruling or plot revenge.
Four notable residents are described in detail (you will, of course, have to supply whatever game mechanics your chosen ruleset requires). One is a local coffee farmer, one claims to be a madman (but is he?), one - the owner of the King's Club - is a rogue of a peasant who tricked his way onto a throne and was ousted from it, and the last is a merchant who trades in coffee.
Then there are some 'situations' which could lead to adventure. You'll have to develop them before they are ready for use, but a slection of twists present different options you can weave into your plots. Everything from dealing with exiled monarchs to assassins to double-dealing in coffee futures, and that's before you get to the human interest that often forms the best stories, no matter the epic sweeping events that might affect whole kingdoms. Some provide work for enterprising characters, others just involve them whether they like it or no.
A couple of magic items, and a selection of rumours and encounters round it all off. There is also a sketch of the centre of the market, showing the few permanent structures and an idea of the temporary ones set up by visiting farmers and traders, who ebb and flow with the seasons.
Find a suitable location in your campaign world and let the dealing begin! Plenty of scope for adventure here...