Odd world but lets have a look.
X starport. A flat dirt patch with a beacon powered by nuclear decay the scouts drop off decades ago.
.3 Gravity, small world. Plants and animals are going to be taller since they can be. Forests of spindly trees towering high in the air, plants and bushes over head tall. Large flying creatures (think pteradac size due to the low gravity also thin atmo would require large wing sizes). Or the world atmo could be low but the deep valleys or river valleys could have higher pressure due to being below sea level if the world had seas.
What are you setting the solar distance at, what about the rotation rate. In the goldilocks zone it could be near frozen or tropical. Inner edge hot and humid, very small ice caps. Possibly a lot of water in the air, small world with active earth movement could be peaks and valleys, rain forests in the valleys and dry tundra on the high areas. Distant and cold would be large ice caps, rest of the world very dry aside from maybe a few deep gullies caused by major rivers fed by glacier melt off. Most of the water trapped in the poles would lead to a few Nile deltas at the equator in deep valleys with a dry cold world elsewhere.
Population of billions with tech 0. How do they feed themselves? The world must have extremely fertile soil to support low tech agriculture. They are stone age and yet there are billions of them. Are there vast forests of fruiting bushes, is the world over run with dog sized rabbits to allow a billion stone age hunter gathers to exist. Depending on temp and world layout are those people spread over huge areas or tight in a few deltas.
Representative democracy and stone age. No communications, no contact with distant areas. Family and tribal groups. Maybe family heads are part of a tribal council that meets a few times a year.
Ok options.
The native sentiments are Stone Age herbivores. Its the only way to have a population of billions. Think families of 10-20, clan groups of hundreds and entire tribes of thousands. Nomadic because they rapidly eat an area clean due to numbers. Tall skinny, multi legged, primitive tool users. Depending on how active the worlds tectonics are or had been the world could be vast plains or valleys. A single vast ocean or many lakes set in a single landmass. Close to the sun the world could be savannah (think African planes), far away and its Siberian tundra.
If you want rain forests you will need closer and hotter, so more water free and small ice caps. Low rain falls except in areas that trap the air moisture such as low valleys surrounded by mountain ranges or the deltas I mentioned above.
The locals could be omnivores with prey creatures or they could be prey themselves and ignore the small animals. Perhaps big cat like pack hunters or raptor like much feared reptiles that inhabit the lower hot areas like the rain forests. Stone age creatures would have major problems with big raptor type pack hunters. Maybe lots of flying stuff. If the locals are horse sized or bigger then humans would make an easy snack to flying hunters with 30 foot wing spans, perhaps the native young or other prey animals are human sized and therefore an easy meal.
With a lot of flying hunters air raft travel will be fun. A small world close to the sun, earth shakes and quakes could be common. A multi legged locals are more used to these. Thin air would lead to much larger lung sizes and barrel chests. PCs on a world where they need oxy pills, or breathers, 33% gravity and earth tremors are going to have fun running from flying hunters.
The locals could cover vast distances fast, say a base speed of 12-15mph and running all day at 25mph+. Annual meetings of the tribal elders could be a 1000+ miles away and the elders could spend a week getting there for the council of the people. So the tribes leaders would be away for up to a month each year. Do the males lead and the females have charge for that month, do the females lead and the males are in charge for the council month till the females return and stop the wars that the males start when left alone. Is this the main mating season where the females go to council while the males fight each other for dominance then mate when the females return. Bound to be a lot of interesting local customs to trip over there :lol:
What are the players doing there. Is it trade. It cannot be worth that much or the megacorps would be there. Perhaps uncommon herbs of plants with unusual properties. Maybe rich hunters go there to hunt the nasty ground hunters and some of the locals near the starport provide guides for the once a year visit by the small star walkers who want to face the great claw hunters of the jungles.
