Campaign:SUPER ROBOT WARS Ω/Mercury

Mercury is a sparsely inhabited world, most of the population living in shielded, domed cities, many of which can move on tracks or jets. Each is a city-state with a reasonable amount of independence, and the planet on its whole is ruled by a council of representatives from each city.
Most of these cities are mining installations, extracting metal from the rich underground of Mercury. Mercury mostly exports all kinds of metal and metallurgic products and technologies, and energy (harnessed directly from the Sun via vast valleys filled with solar panels and bounced from satellite to satellite via microwaves).

Most of Mercurian technology is strong, armored, sturdy, rugged and built to last and to withstand. Metal is in no short supply, after all. Their armed forces are divided by city-state.

Mercury houses the second-largest psionic academy (after the one on Luna), the Hermetic Academy, boasting strange, quasi-magical traditions and esoteric practices tied to ancient mythology, in contrast with the Tranquility Valley's rigid and scientific approach

Politically, the city-states are all in the Mercurian League, a loose military and commercial alliance, but retain most of their independence.