Umnub was the smaller of the two moons that orbited the world of Sullust, on the Outer Rim Territories of the galaxy. It was incapable of supporting life, but the moon was mined for ores and minerals during the height of the Galactic Republic by the Sullustans. The mines finally played out approximately a thousand years before the outbreak of the Galactic Civil War; as a result, the facilities were then abandoned.