The old metropolis world of Contri was once a bustling and proud monument to the peoples who lived there. A single, overgrown cityscape sprawls across the entirety of the planet -- casting most of its streets in the shadows of its skyscrapers.
The lava mining planet of Gelga is hardly hospitable to most creatures -- its atomosphere comprised of mostly noxious fumes and combustible gasses. However, deep beneath its magma oceans sits a pool of a rare and extremely useful element.
Thora hosts an interesting landscape, as most of the world is comprised of caves located deep beneath the surface. Above these cave systems sit the skeletons of spires that once were used as operating and housing units for whoever lived there.
Bromea is a desert planet mostly covered in an intense sandstorm, only offering sunlight approximately 2 hours every month. Scattered across this barren landscape, however, are highly advanced outposts that are each large enough to house a small colony.
A planet whose entire surface is inhabitable, so the progenitor civilzization built their cities below ground. Thousands of miles of a sprawling metropolis occupies the husk of this system; leaving plenty of places for critters and squatters to take refuge.
A small moon whose surface has been infested with some sort of fungal growth. The crystal spores are brittle to the touch, but break into hundreds of particles. Once they land, they grow instantaneously, leaving a haunting yet beautiful graveyard in its wake.