Question: It's for an RPG worldbuilding blog I'd like to make.

Answer: 
[stage](https://en.wiktionary.org/wiki/stage)
---------------------------------------------

> 
> * A platform, generally elevated, upon which show performances or other public events are given.
> * A degree of advancement in a journey; one of several portions into which a road or course is marked off; the distance between two places of rest on a road
> * *(video games)* A level; one of the sequential areas making up the game.
> 
> 
> 

Consider the term "to set the stage" in a broader context than that of a theater. Shakespeare often used this term for when narrators introduce plays. RPGs are games of storytelling and are quite similar to plays, and they often use theatrical terms.
Here are some ideas to get you thinking about what works with your project:

Environment, locale, mise en scène, backdrop, curtain opening, tableau (this one has a fun plural -- tableaux), country, chessboard, playmat, gameboard, terrain, land.