The four great moons of Jupiter—Ganymede, Callisto, Io, Europa—heart of the Rim and the arena where Darrow means to break the Sword Armada.
Ilium is the collective name for Jupiter's four great Galilean moons—Ganymede, Callisto, Io, and Europa—the industrial and political heart of the Rim, ringed by two of the greatest fleets in the system: the Moon Lords' armada and the Sovereign's Sword Armada sent under Roque. Metropolitan Ganymede is the Rim's center and its unrivaled dockyard; Io is its breadbasket. When the Rim's children escaped Luna and Revus au Raa's heirs seized the Calisto garrison fleet, Romulus au Raa was elected Sovereign of the Rim and the Second Moon Rebellion began.
Judging that beating the Jackal on Mars would take a bloody decade, Darrow resolves to leave Mars entirely and strike here instead—hiding his fleet on the barren moon Sinope to fall on Roque's Sword Armada and 'rip the beating heart out of the Society war machine.'
The four vast Galilean moons swimming around Jupiter's marbled face—farm-decked Io's sulfur seas, metropolitan Ganymede's dockyards, ice-crusted Europa and Callisto—amid dueling fleets and shielded cities.
The Jovian theater of the war; the Rim's heartland and the arena where Darrow gambles everything to destroy the Sword Armada.