Welcome to Rasmussen’s Guide, a tool for those wanting more science in their science fiction.
It is for GMs running campaigns who need an alternate world with a logical ecology. Admit it, game worlds need internal logic, after all. Living animals do not spontaneously generate from nonliving matter, nor do they magically appear out of thin air. All living things metabolize, reproduce, grow, and adapt. They do not do these things in a vacuum. This planetary guide is a concise look at these lifeforms as they might evolve on a variety of planets, moons and celestial objects, using each world’s surface gravity to define its primary vertebrate Superclass and maximums.
From space at a distance, a white atmospheric haze surrounds the Moon El Dorado. On a closer look from orbit, El Dorado has two atmospheric polar vortices over the moon’s north and south poles. The swirling gas cloud is a mix of colorless hydrogen chloride (HCl) that forms white fumes of hydrochloric acid when contacting atmospheric humidity. Seen through the clear vortices, the world is silvery with white dunes. White clouds partially obscure metallic continents surrounded by white seas. Upon closer examination, seasonal hydrochloric acid rainstorms produce wet patches visible from orbit. At the surface, the sky is a thick, white smog. The surface not covered in white dunes appears silver, with gold, yellow, and copper metal boulders and rocks. The plentiful boulders are heavy metals coated in fine, white powder.