A six-city industrial refuge carved beneath Europa's sea, the Deep is Athena's heavily armed sanctuary and the intended last shelter from Fá's coming assault.
The Deep is a network of six cities beneath Europa's ocean, carved into the moon's solid core. It began as mining infrastructure before evolving into an industrial, research, and weapons-manufacturing complex, making it far more than an underground civilian shelter.
Athena has seized all six cities as the surrounding Jovian defenses fail. With Io lost, Callisto suffering atomic attack, Ganymede behind orbital shields, and Europa's sea cities exposed, the Deep becomes her chosen redoubt. Cheon says its sealifts will be destroyed once an enemy breaches Europa's atmosphere, leaving an invading Obsidian force unable to reach its depths.
The plan promises safety for the evacuees aboard the Archimedes, but it also leaves the floating surface cities outside the sealed refuge. Aurae's hope that the Deep can protect everyone meets Cheon's harsher acknowledgment that the fate of those above is Athena's decision.
Six linked subterranean cities carved into Europa's rocky core beneath the Discordia Sea, combining deep mining chambers, industrial works, laboratories, weapons production, and sealift access to the surface.
The Deep is the Daughters' strategic refuge, a place of real security and armament whose defensive logic may demand that Europa's surface be abandoned.