Extreme Environments
Aerial: A world might include windy realms of floating islands and castles in the clouds, or form a swirling gas giant.
Alien: Encompassing all manner of unique environments, alien environments represent biomes prevalent to a specific world or even those we haven't yet pondered could exist. Examples could include a vast sea of self-replicating crystal or a world where the landmasses and water shift into different states of matter at irregular intervals.
Glacier: Massive sheets of dense ice constantly moving under their own immense weight, glaciers are frozen wastelands riddled with columns of jagged ice and snowcovered crevasses.
Gravity: Both high- and low-gravity environments present opportunities for fantastical ecologies and challenges for visitors. See page 98 for more details on these environments.
Radioactive: Whether barren wastes or abandoned cities, these environments frequently feature mutated flora and fauna, pools of acid, and radioactive materials that can overwhelm even higher-level environmental protections.
Underground: Some worlds have deep natural caverns, while others have extensive winding tunnels and expansive realms below the surface.
Undersea: A subset of aquatic environments, undersea environments are those areas submerged beneath the waves.
Vacuum: Worlds without breathable air are either deserted wastelands or otherwise occupied only by constructs,undead, and cosmic beings often too alien for most mortals to understand.
Virtual Reality: Your world is entirely digital. Your players can only ascertain this truth over time via hints, and whether or not the entire planet's population is trapped in a virtual space, or the entire universe is a simulation, can depend on the campaign's scope and theme.
Volcanic: Hellish landscapes of molten lava, burning ash, and scorching temperatures pose immediate danger.