The Setting…
You all are from a group of islands named something or other in some part of some world. There’s maybe, like, one small city on one of the islands, and then a lot of villages on all the surrounding islands. This area is basically your known world, and the problem is you’ve seen all of it.
You all grew up here, and obviously, it’s a seafaring community, so you all know the basics of sailing, shipbuilding, fishing, etc etc etc.
You know that there are other places, because occasionally merchant ships come through with people who talk funny/look funny/sell funny things, all that good stuff. But wherever it is they come from it’s far away. All you know is that they come from other groups of islands that are past the horizon in various directions.
As far as anyone knows the whole world is made up of small groups of islands like this one. And most people spend their whole lives in the same group of islands they grew up in. A few adventurous souls travel between, but it’s rare, and frowned upon. The routes between the groups of civilizations are jealously guarded secrets, and most such people have to start off with no idea where they are going. No surprise then that most are never seen again.
There are also rumors and stories of a “mainland” somewhere. You’re not actually sure what a mainland is, from the descriptions you picture it as just a big island. There’s an old man on the island who says he knew a man once who had seen the mainland. But he tells lots of stories, and the villagers think they are just that, stories. But the old man swears this one is true, and you’ve always wondered…….