Mirth
Blue skies, warm weather, and ancient metropolises-Mirth is humanity’s original home. The planet plays host to billions of humans across seventeen diverse nations. The planet has been settled for thousands of years which is a stark contrast to the planetary colonies which are no older than 50 years.
The nations of Mirth have their own politics and cultures and exhibit all sorts of relationships with each other (including alliances to uneasy truces). These attitudes tend to bleed outward to the colonies since they start out as extensions of one nation (or an alliance of nations). While knowledge of Mirth isn’t mandatory in order to have an adventure, the planet Mirth and its nations do serve as a handy dispenser for villains, motivations, ancient roots, and other plot devices.
