The Underworld of Aleen was created millennia in the past as the arbozoic trees which dotted the surface grew, died, and decayed. Their expansive root systems, once desiccated, left behind massive caverns in the upper crust of the planet where a unique atmosphere formed and the Kindalo species evolved. Additional tunnels were created as water, lava, and tectonic plates moved below the surface all across the planet. Because of the tectonic activity, the separate atmospheres of the planet confused planetologists from the Galactic Republic and later the Galactic Empire. The Great Seal was designed by the Aleena to symbolically close off the Underworld to the surface dwellers as a compact between the two races of the world.
The government within the Underworld was unique to the Kindalo. Practicing a type of absolute consensus, the Kindalo required all members of their species to vote on matters of import in order to take action. Action required a unanimous agreement by all members of the society, which caused xenobiologists and political theorists from offworld to speculate that the Kindalo species was extremely small. The Underworld was also home to the mysterious being called Orphne. Encountered rarely by visitors throughout the planet's history, Orphne resided within her own domain within the Underworld.