Cosmology
Source GM Core pg. 138
Before designing your campaign's first world, you should first consider the nature of its larger system and what that might mean for the planet. While most traditional heliocentric star systems like the Pact Worlds make developing your world as straightforward as taking cues from the real world, other system compositions are possible, either through quirks of physics or the intervention of powerful deities. Other alternatives to traditional heliocentric star systems can be found under Composition of Space.
The Universe
Source GM Core pg. 138
The reality in which mortals live out their short existence is known to sages and scholars by many names—the Universe or material reality, among others. The structure of the physical universe might adhere to any of the following models, or it might be something completely different.
Endless: The universe is an unimaginably sparse void of infinite space, littered with stars, planets, and various detritus.
Limited: The physical universe in your campaign world might be smaller in scope yet far more fanciful. For example, Norse cosmology describes nine worlds connected by an immense ash tree. How does that fit into your science fantasy story?
Bizarre: Sometimes the universe is more complex than the previous two categories, or possibly nested within multiple realities and timelines. What if the universe the PCs first know is in fact a magical or technological simulation of such complexity that its inhabitants are unaware that they exist as an artificial consciousness? Perhaps this is even where your PCs first meet before transitioning into another reality.
Endless: The universe is an unimaginably sparse void of infinite space, littered with stars, planets, and various detritus.
Limited: The physical universe in your campaign world might be smaller in scope yet far more fanciful. For example, Norse cosmology describes nine worlds connected by an immense ash tree. How does that fit into your science fantasy story?
Bizarre: Sometimes the universe is more complex than the previous two categories, or possibly nested within multiple realities and timelines. What if the universe the PCs first know is in fact a magical or technological simulation of such complexity that its inhabitants are unaware that they exist as an artificial consciousness? Perhaps this is even where your PCs first meet before transitioning into another reality.
Composition of Space
Source GM Core pg. 139
Whether the primary setting of your campaign or an avenue between worlds, the nature of outer space is as malleable as the rest of your cosmology.
Celestial Spheres: The ancient Greeks posited that planets, stars, and more were embedded like jewels within celestial orbs of quintessence nested within one another. Perhaps celestial bodies in your campaign are really massive aeon stones, or something else unique to your setting.
Endless Sky: What if the blue sky overhead extended outward forever? One need only fly high enough and far enough to reach another world, using environmental protections to defend against the frigid cold. In such a campaign, space might not carry the hazards of radiation and breathlessness, but it might be more like a vast sea where ships and people flow with the currents and explore the depths.
Vacuum: In conventional astronomy, outer space is an immense void existing in a near-perfect vacuum. The immeasurable expanse of space is home to everything in the Universe and requires starships to both navigate and survive. You might incorporate hard sci-fi details to make adventures in outer space feel more believable and perilous.
Celestial Spheres: The ancient Greeks posited that planets, stars, and more were embedded like jewels within celestial orbs of quintessence nested within one another. Perhaps celestial bodies in your campaign are really massive aeon stones, or something else unique to your setting.
Endless Sky: What if the blue sky overhead extended outward forever? One need only fly high enough and far enough to reach another world, using environmental protections to defend against the frigid cold. In such a campaign, space might not carry the hazards of radiation and breathlessness, but it might be more like a vast sea where ships and people flow with the currents and explore the depths.
Vacuum: In conventional astronomy, outer space is an immense void existing in a near-perfect vacuum. The immeasurable expanse of space is home to everything in the Universe and requires starships to both navigate and survive. You might incorporate hard sci-fi details to make adventures in outer space feel more believable and perilous.
The Barycenter
Source GM Core pg. 139
A star composes the center of most solar systems, which develop planets from the detritus following the collapse of a nebula or other cosmic shock wave. In a binary star system, the barycenter of a system is likely the center point between the two rotating stars. Erratically shaped systems can shift the barycenter away from the center of gravity, whether by recent cataclysm or proximity to another source of gravity. A supernatural collapse of a solar system's star could even result in a black hole developing at the center of a cluster of doomed planets, entire generations passing in the eternal darkness only to one day be consumed by their dead star. What lies near the barycenter of your galaxy? Does anything reside there, mortal or otherwise? How do the civilizations in your setting view the construct that keeps their worlds in place? There are effectively three options for most settings.
Dyson Sphere: Perhaps a solar system has been enclosed in an artificial structure designed to harness the power of the sun. The residents have long since forgotten, and escaping the sphere is an eventual goal of the campaign.
Geocentric: What if another world was the center of the known universe? Perhaps it's the primary game world, or perhaps it's the campaign's final destination.
Heliocentric: Physics dictates that all planets in a system orbit the sun, and the center of mass of a galaxy orbits a black hole. Some systems might have more than one star.
Dyson Sphere: Perhaps a solar system has been enclosed in an artificial structure designed to harness the power of the sun. The residents have long since forgotten, and escaping the sphere is an eventual goal of the campaign.
Geocentric: What if another world was the center of the known universe? Perhaps it's the primary game world, or perhaps it's the campaign's final destination.
Heliocentric: Physics dictates that all planets in a system orbit the sun, and the center of mass of a galaxy orbits a black hole. Some systems might have more than one star.