The asteroid belt between Mars and Jupiter, home to millions of workers and their descendants who mine ice, ore, and volatiles for the inner planets. Belters live on spinning stations like Ceres, Eros, and Tycho, or in ships and smaller rocks scattered across a vast arc of space. Generations of low gravity have reshaped their bodies - taller, thinner, with larger heads and brittle bones that make Earth's gravity a death sentence. Economically dependent on Earth and Mars for food, air, and water, the Belt exists in a state of perpetual exploitation dressed up as commerce. Its people have developed their own creole language, hand gestures for use in vacuum suits, and a fierce collective identity forged by shared hardship. The OPA (Outer Planets Alliance) gives political voice to Belter grievances, though its factions range from legitimate labour organisers to radical separatists. The Belt's strategic importance shifts dramatically after the opening of the ring gates, when thirteen hundred new systems offer resources without the need for Belter labour.