Location from Red Rising by Pierce Brown
Volcanic moon of Jupiter and seat of the Rim Dominion. Home of the austere, militant Golds who rejected Core decadence and built their own civilization at the edge of the system.
Io is what Gold culture looks like without the decadence. The Rim Golds settled the outer planets generations ago and built a society that kept the martial discipline of early Gold civilization while shedding what they saw as Core corruption — the Pinks, the excess, the political games. Romulus au Raa governed from Io with a council of equals rather than a Sovereign's autocracy. The Rim fights differently too: their ships are built for endurance rather than shock, their warriors trained for patience rather than glory. Io's volcanic landscape shaped its people — they are hard, spare, and they endure. When the Core's wars finally spilled outward, Io became the fulcrum. The Rim had ships, warriors, and a grudge against both the Society and the Rising. Whoever won Io's alliance would tip the balance of the entire system.
A sulfurous moon of active volcanoes, lava flows, and radiation-shielded cities built into the rock. The architecture is stark and functional — no Gold excess here. The sky is dominated by Jupiter's massive presence overhead, painting everything in bands of amber and ochre light.
Also known as: Io, the Rim seat, Raa stronghold