Oso IV is a terrestrial planet in the Oso system, and is the fourth planet from its sun. Lacking a core, it has an undifferentiated interior that is rich in a wide variety of minerals. Soldiers from the nearby United Empire of Earth UEE) Army observation base Chimera must keep Oso IV under guard to prevent rogue mining operations from forming there. In 2877, the Army made its largest arrest when they discovered an underground mine in the equatorial region that had been in use undetected for over 3 SEY.