A Primer on Lucidia
World Setting
The world of Lucidia is a wide, vast, smorgasbord of different cultures and powers. Different areas of the land, you see, have different Affinities to various powers. Technology might be limited to the bow and arrow, while the next valley over could deal with lasers and antigrav. However, moving to that first valley the lasers wouldn't work, and firing into it they wouldn't either. Similar things happen with magic, psionics, and several other types of energy as may be convenient for a GM. Kinetic attacks, like bullets or rocks, seem to be more universal, though things like supersonic designs are more likely to falter mid-flight and slow to local Affinity's levels.
This does, though, result in somewhat strained trade relations. The basics are exchanged well enough, but individual city-states don't have a unified government between them, and typically resort to gold as a trade medium. You normally get along well enough with your neighbors, but are often wary of stuff that works there, but not where you grew up.
It is also likely to be a source of major confusion for anyone transitioning from a different realm, as traveling to other cities might cause their devices, magic, or psionics to stop working.
Artifacts
Within Lucidia, there exist certain objects that alter the reality of the land just enough to suit their purposes, and nothing else. It might be a magical wand that can project a fireball where one would not otherwise operate, or a laser gun that can fire in a land of sticks. Whatever their nature, the application of these tools has led many dictators to enjoy a highly favorable rule... and also led many an adventurer through a crusade against them. They come in many forms, and are generally regarded as the production of some form of nightmare demon.
One key attribute of an Artifact is that they convey the ability to use them to their weilder, and such knowledge doesn't stick around after losing it. If you know how to use an energy sword the instant you pick it up, or even know that the small black object is an energy sword, you have an Artifact.
Worldsetters
The worldsetters are artifacts of a different nature, which exist and alter reality on a wider scale. Perhaps a region has no magical Affinity naturally, but such an object might allow it. They're generally found in places where their effects would be necessary to make life livable, and much more mysterious than plain everyday Artifacts.
City-State of Lucidia
The City-State of Lucidia, often called Lucidia City, is perhaps the most solid non-totalitarian government available. Many diverse groups have been brought together, forming a solid unifying super-culture while keeping individual sub-cultures rich and thriving. This has helped with their trading relations with nearby city-states, allowing like-minded groups to talk to representatives. The Crown of Lucidia is responsible for this, a keen political force with more years of experience than many can comprehend. With Lucidia City's presence in a more or less "everything goes" realm, it also helps that the Crown can handle any powerful threat, while maintaining a highly trained, equipped, and competent City Watch to keep any typical troubles foreign or domestic handled. Typical troubles handle most anything up to orbital bombardment, dieties running amock, and such - those, the Crown can handle, and will handle with extreme prejudice.
Many locations that were in Anycity have managed to re-appear within Lucidia City, and it's becoming increasingly obvious that you're not in Kansas Anycity anymore. Technology is mostly at the level of modern day, though mostly because it's convenient and easy for most groups to handle. There are pockets of higher, and lower, technology. Magical usage can also be considered an average, day-to-day affair.
The Chat
The bar that is commonly called The Chat exists within the boundries of Lucidia City's control, some distance away from the proper city edges, at a point where energies from other realms commonly arrive. However, it is increasingly on the patrol route of the City Watch, and flagrant activities should be considered as coming to the attention of the City Watch.
Conflict
As mentioned earlier, conflict across Affinities is difficult, but not impossible. Shells still carry their kinetic force, although perhaps slowed down significantly if they rely on special coatings, hypersonics, or such. Common tactics that don't deal with Artifacts for technological forces involve producing relatively superior devices within your own realm, then sending specifically trained squads into your neighbors. Similarly, though, you often end up dealing with a group of trained mages that can mow you down like a peasant uprising, which limits effectiveness. Comprehensive warfare is a detailed, serious, and involving concept.
Unfortunately for those who engage in such highly detailed and thorough planning, it's also often trumped by a plucky hero with an Artifact he found in his field one day while plowing.