Progression

From Wikidsouls

Demon's Souls straddles the line between a linear game and one with an open world environment. After completing the game's tutorial stage, you'll find yourself in the Nexus, the game's hub world. The Nexus contains five archstones, portals to the various regions of the Boletarian kingdom. Upon first arriving in the Nexus, you will only have access to Boletarian Palace's archstone. You will need to clear the first stage of this archstone (commonly known as 1-1) before being able to progress anywhere else, but after doing so, the game will lose the linear feel and will leave the player with more options as to how they want to progress. Once this first stage is cleared and some duties in the Nexus are taken care of, the other four archstones will open up, allowing you to choose your next point of venture. Each archstone region spans three stages, with the exception of Boletarian Palace, which adds a fourth. You'll progress from stage to stage within each region linearly but at any point can return back to the Nexus and travel through any of the other archstones. Once the final stage of each archstone is complete, you'll be able to progress to the game's final event.