Planetary Basics
Source GM Core pg. 139
When designing the physical features of a campaign world, you'll want to determine its shape and the general distribution of landmasses. You should also establish the world's size relative to its neighbors, though the importance of a planet is rarely relative to its mass.
Shape
Source GM Core pg. 139
In a science-fantasy setting, the shape of your world need not be spherical as governed by the laws of physics. It could take on any shape you desire, and it might not be a planet at all!
Globe: Barring some catastrophe, worlds in our reality are roughly spherical due to the influence of gravity.
Hollow World: What if the landmasses and civilizations of a world existed on the inner surface of a hollow sphere? In such a world, the horizon would climb upwards, permitting creatures to see landmarks at extraordinary distances. A vast civilization might inhabit the interior of the world, lining the outer edge with solar panels for renewable power. Light might emanate from a sunlike orb in the world's center, from various other natural, technological, or magical sources, or not at all.
Irregular: What if your world is flat, a toroid, or shaped into a cylinder, cube, or other polyhedron? What if it's something even stranger? With such an unusual shape, you need to decide how gravity, atmosphere, and other details function. These types of irregular shapes can also include asteroids, colony ships, and space stations.
String: The world might be something entirely unique, like a stellar waterway akin to the River Betweena chain of stellar debris each a mini-world in its own right, or even a planetary ring detached from its maiden world and cast into the void.
Globe: Barring some catastrophe, worlds in our reality are roughly spherical due to the influence of gravity.
Hollow World: What if the landmasses and civilizations of a world existed on the inner surface of a hollow sphere? In such a world, the horizon would climb upwards, permitting creatures to see landmarks at extraordinary distances. A vast civilization might inhabit the interior of the world, lining the outer edge with solar panels for renewable power. Light might emanate from a sunlike orb in the world's center, from various other natural, technological, or magical sources, or not at all.
Irregular: What if your world is flat, a toroid, or shaped into a cylinder, cube, or other polyhedron? What if it's something even stranger? With such an unusual shape, you need to decide how gravity, atmosphere, and other details function. These types of irregular shapes can also include asteroids, colony ships, and space stations.
String: The world might be something entirely unique, like a stellar waterway akin to the River Betweena chain of stellar debris each a mini-world in its own right, or even a planetary ring detached from its maiden world and cast into the void.
Composition
Source GM Core pg. 140
While most habitable home worlds are assumed to be terrestrial planets like Earth, in a science-fantasy setting the only limits are your imagination, and each change presents new options for far-reaching cultural and technological innovations. Some worlds combine these compositions, such as the tidally locked world of Verces that's half frozen from a lack of sun and half searing from intense solar activity, with a ring of cities separating the two extremes.
Barren World: These barren worlds include asteroids and desert and rocky planets unable to support life on its surface. Residents are often from other worlds or spend most of their lives struggling to survive. Some of these worlds have evolved intelligent life capable of handling the extreme circumstances. They include worlds that once teemed with life that has since been destroyed by war or some other invasive force, like the husk worlds left behind by the Swarm or the once-living planet of Eox. In many cases, the composition of the world is completely bizarre, such as a world composed entirely of crystals!
City World: Also known as an ecumenopolis, this planet-sized city completely covers the surface of the world, often spanning even the vast and often polluted oceans that once supported life on the overly developed world. These planets likely have several superstructures visible from space but are otherwise vast monuments littered with lights. It could've been built on a moon or asteroid, perhaps as a colony from another nearby world. While these worlds are often the most populated, they also frequently have the least variety of life (at least in terms of plants and animals) and could even be mostly abandoned due to a planetwide catastrophe exacerbated by its sprawling monoculture. A city world is likely to be or have once been united under a single nation-state, even if it's now divided into multiple city-states or rival districts. Oftentimes, the planet forms slums near the surface while the wealthy live atop skyscrapers or in floating arcologies high up in the atmosphere where they're safe from pollution and noise.
Constructed: Constructed worlds didn't form naturally but were built by their inhabitants using natural or synthetic materials. A constructed world could be an inhabitable space station, a massive worldship, or a terraformed satellite resembling a real planet. Examples in the Pact worlds include Absalom Station and the Idari.
Gas Giant: These enormous worlds are often circled by countless moons large enough to support entire campaigns. Some, like Bretheda, have cities floating atop or within the gas. Others float along the ring of these worlds, the composition of which can hint at the world's history. Perhaps some creatures can survive on the surface of these worlds, protected by eternal storms too violent for most spaceships to navigate. The substances of these worlds are often harvested for interplanetary trade.
Ice World: Ice and snow cover these frigid worlds often found on the fringes of a star system. Cities frequently develop inside of mountains or atop enormous thermokarsts, regions replete with hollows like the Ice Wells of Aballon, that offer a reprieve from the eternal cold. Perhaps the only known structure in these worlds is a single research or military station operated by a skeleton crew, or perhaps the residents thrive in the frigid wastes or live in aquatic cities submerged under the miles-thick ice.
Lava World: Volcanic plumes of lava and smoke cover these worlds, often controlled by one or more mining companies looking to exploit the rare starmetals and other resources left undisturbed on these often lifeless planets. What kind of life could develop in these worlds? How might they react to being exploited by alien miners? And what valuable resources and treasures might await those who can survive in such a hostile environment?
Lush World: Forests, jungles, or swamps cover these worlds. Whether natural, supernatural, or the result of terraforming gone awry, these worlds often have civilizationending threats, like colossi, that prevent their unspoiled nature from being exploited and their surfaces from rampant development. Perhaps these threats might not be as obvious as giant monsters and could very well be surges of primal magic, random boiling geysers the size of cities that sustain the verdant paradise, or microbial threats that can bypass even the highest-grade environmental protections.
Terrestrial: These Earth-like worlds include oceans and continents with all the variety you'd expect on a habitable surface. The planet itself could've been terraformed with technology or magic necessary to keep it from becoming another type of world.
Water World: A world composed of or submerged in planet-spanning oceans could include a smattering of islands or floating settlements. Is the world surrounded by pristine blue seas, or is the water green due to continentsized algal blooms? Perhaps the liquid isn't even water but instead a substance that either makes the planet a center of the galactic economy, or it's a cursed world avoided and shunned by the rest of the galaxy.
Barren World: These barren worlds include asteroids and desert and rocky planets unable to support life on its surface. Residents are often from other worlds or spend most of their lives struggling to survive. Some of these worlds have evolved intelligent life capable of handling the extreme circumstances. They include worlds that once teemed with life that has since been destroyed by war or some other invasive force, like the husk worlds left behind by the Swarm or the once-living planet of Eox. In many cases, the composition of the world is completely bizarre, such as a world composed entirely of crystals!
City World: Also known as an ecumenopolis, this planet-sized city completely covers the surface of the world, often spanning even the vast and often polluted oceans that once supported life on the overly developed world. These planets likely have several superstructures visible from space but are otherwise vast monuments littered with lights. It could've been built on a moon or asteroid, perhaps as a colony from another nearby world. While these worlds are often the most populated, they also frequently have the least variety of life (at least in terms of plants and animals) and could even be mostly abandoned due to a planetwide catastrophe exacerbated by its sprawling monoculture. A city world is likely to be or have once been united under a single nation-state, even if it's now divided into multiple city-states or rival districts. Oftentimes, the planet forms slums near the surface while the wealthy live atop skyscrapers or in floating arcologies high up in the atmosphere where they're safe from pollution and noise.
Constructed: Constructed worlds didn't form naturally but were built by their inhabitants using natural or synthetic materials. A constructed world could be an inhabitable space station, a massive worldship, or a terraformed satellite resembling a real planet. Examples in the Pact worlds include Absalom Station and the Idari.
Gas Giant: These enormous worlds are often circled by countless moons large enough to support entire campaigns. Some, like Bretheda, have cities floating atop or within the gas. Others float along the ring of these worlds, the composition of which can hint at the world's history. Perhaps some creatures can survive on the surface of these worlds, protected by eternal storms too violent for most spaceships to navigate. The substances of these worlds are often harvested for interplanetary trade.
Ice World: Ice and snow cover these frigid worlds often found on the fringes of a star system. Cities frequently develop inside of mountains or atop enormous thermokarsts, regions replete with hollows like the Ice Wells of Aballon, that offer a reprieve from the eternal cold. Perhaps the only known structure in these worlds is a single research or military station operated by a skeleton crew, or perhaps the residents thrive in the frigid wastes or live in aquatic cities submerged under the miles-thick ice.
Lava World: Volcanic plumes of lava and smoke cover these worlds, often controlled by one or more mining companies looking to exploit the rare starmetals and other resources left undisturbed on these often lifeless planets. What kind of life could develop in these worlds? How might they react to being exploited by alien miners? And what valuable resources and treasures might await those who can survive in such a hostile environment?
Lush World: Forests, jungles, or swamps cover these worlds. Whether natural, supernatural, or the result of terraforming gone awry, these worlds often have civilizationending threats, like colossi, that prevent their unspoiled nature from being exploited and their surfaces from rampant development. Perhaps these threats might not be as obvious as giant monsters and could very well be surges of primal magic, random boiling geysers the size of cities that sustain the verdant paradise, or microbial threats that can bypass even the highest-grade environmental protections.
Terrestrial: These Earth-like worlds include oceans and continents with all the variety you'd expect on a habitable surface. The planet itself could've been terraformed with technology or magic necessary to keep it from becoming another type of world.
Water World: A world composed of or submerged in planet-spanning oceans could include a smattering of islands or floating settlements. Is the world surrounded by pristine blue seas, or is the water green due to continentsized algal blooms? Perhaps the liquid isn't even water but instead a substance that either makes the planet a center of the galactic economy, or it's a cursed world avoided and shunned by the rest of the galaxy.