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Marsh

Source Galaxy Exploration Manual pg. 68
Wet, smelly, and buzzing with flies—the stereotypical marsh is hardly an attractive destination. But this image ignores the breadth of how wetlands manifest and overlooks the incredible biodiversity of alien quagmires, where the possibilities of life remain virtually endless.
Marshes can range from herbaceous territory of towering grasses that can hide any threat to swamps with shadow-casting trees—and far beyond. Do explorers trudge through the peaty sludge of a bog or clamber up a fen’s far drier inclines? Even riparian zones like riverbanks, flood plains, and estuaries meet the core criterion: consistently waterlogged soil. Add to that the wide range of temperatures of these marshes—from tropical mires to tundra that periodically thaws into ice-cold ponds—that provide a vast number of narrative and descriptive options.
Wetlands are a literal slog to navigate, and those on foot endure the boot-sucking mud while brushing aside sheets of stubborn hanging moss and slapping away insistent insects. Marsh travel can also feature unusual vehicular travel: from explorers piloting fan boats while cruising an uncharted bayou to river pirates fleeing pursuit in a daring hovercraft chase.
Common features of Earth-like marshes can become wild and strange when encountered in alien ecosystems. Under a blue sun, predatory rainbow eels the size of tree trunks undulate through the dark water, ominously rocking orange lily pads as they search for their next meals. The water pressure and surface tension on one high-gravity world can be so intense that foot-thick rafts of algae choke the mires, creating floating bridges stable enough to support an all-terrain buggy. Grasses in a low-gravity marsh may loom 30 feet high, able to hide even tremendous, broad-footed theropods that hunt by scent. Flora on another world produce toxic gases as a byproduct, which pool in dense clouds over the bog waters. Fauna have adapted to clamber and fly above these dead zones, and those who misstep tumble into the oxygen-starved waters only to mummify in the thick peat.
Thankfully, marshes present as many opportunities as dangers. Only a rain forest surpasses a wetland’s biodiversity, and those animal, plant, and fungal resources can be the key to unlocking medical discoveries or simply represent a lucrative delicacy that wealthy patrons would pay well to acquire. While marshes are quick to swallow ruins and hide even the largest starship wrecks, their still waters inhibit decay in a way that makes excavating them one of the best ways to understand the past. And as an imposing biome that most civilizations hesitate to invade, a marsh can be an invaluable sanctuary for those who need to escape the hustle and bustle (and perhaps the arrest warrants) of modern society.
Water shapes life in the wetlands—both through the abundance of moisture and also the seasonal periods when the ground becomes more dry. The most successful inhabitants straddle the line between being fully terrestrial or aquatic. Even nimble arboreal specialists like monkeys and cats must become adequate swimmers. Broad feet keep larger inhabitants from sinking irreversibly into the mud, allowing mid-sized sauropods, bovines, and pachyderms to graze on any foliage that can survive being submerged for months at a time. Many bogs and fens have poor soil nutrients, which drives plants to evolve carnivorous strategies to meet their needs. In an alien environment, these plants can grow to immense size, able to consume virtually any animal they encounter. Sapient non-aquatic inhabitants must contend with the constant wet conditions. For most, that means constructing elevated living spaces—such as woven tree houses built on sturdy platforms—creating floating settlements, or just selectively draining parts of the marsh to reclaim dry land. For aquatic species, seasonal droughts remain a bigger concern, inspiring the creation of artificial reservoirs that remain submerged year-round. Both kinds of sapient creatures benefit from dredging deep channels to form watery highways, with carefully maintained marshes transforming into webs of transit and aquaculture over generations.

Marsh Adventurers

Source Galaxy Exploration Manual pg. 68
Wetlands are fertile grounds for culture, research, and life. Farmers, fishers, biologists, and mariners are all excellent backgrounds for prospective adventurers raised in and around marshes, though more remote regions could as easily attract smugglers, fugitives, or even luddites who disdain the inexorable march of spaceflight and technology. Growing up in the wetlands hones an adventurer’s movement skills to navigate slippery banks and deep water, possibly represented by Athletics and Acrobatics. The wide range of poisonous, disease-bearing, and outright carnivorous organisms paired with the ample natural resources also means that skills like Life Science and Survival are key to reaching maturity.

Marsh Worlds

Source Galaxy Exploration Manual pg. 69
Wetlands are common on terrestrial worlds, yet only a rare few planets are covered entirely by this biome. Such planets often have flat topography that’s conducive to supporting standing water and spongy soils, kept inundated either by consistent precipitation, powerful tides that draw water over vast estuaries, or both. On such worlds, even the rare mountain chains are low, creating rain shadows that channel water into low-lying areas while valleys accumulate steep fens. Because of the diverse range of wetlands, a single-biome planet can support countless varieties of life based on the nuances of drainage, elevation, and soil type, with regional boundaries defined by where bog transitions into swamp, lagoon, or river. Conventional continents might not exist, with dry land instead consisting of peat accumulations a hundred feet thick or greater.
While sapient beings might clear and manage vast aquaculture fields, some animals might dam key waterways and create lakes, while others tear game trails through thick swamps that are then used by countless other organisms. Where societies rise, the combination of perishable materials and unstable foundations mean that ruins swiftly disappear. On tectonically active planets covered by peat and other fuel, lava could spark subsurface fires that slowly burn their way across the world, creating smoldering underground hellscapes that burst upward to consume an entire region before dying out, making way for new growth.

Marsh Rules And Reference

Source Galaxy Exploration Manual pg. 69
Starfinder already provides numerous rules that befit marsh adventures. Basic information appears on pages 397–398 of the Core Rulebook, with an emphasis on navigating shallow bogs and deep bogs. Check out the cover rules on pages 253–254 of the Core Rulebook, as a combination of water and a swamp’s woody vegetation should give creatures in these environments plenty of natural defenses. On those same pages, see the concealment rules to incorporate sheets of hanging moss, mazes of grass, and low-lying boughs into firefights. Wetlands can quickly enter deeper water, where suffocation and drowning (Core Rulebook 404) and underwater combat (Core Rulebook 405) come into play, and marshes often attract disease-spreading creatures that can leave creatures fighting off afflictions (Core Rulebook 414–419).

Marsh Toolbox

Source Galaxy Exploration Manual pg. 70
See Biome Subsections on page 46 for advice on how to use the following tables.

Marsh Inhabitants

D%	Sapient	Threat
1–4	Brenneri	Atlapak
5–8	Cerebric fungus	Caypin
9–12	Copaxi	Colour out of Space
13–16	Dragon, black	Diatha
17–20	Dragon, bronze	Dinosaur, pterosaur
21–24	Entu colony	Dinosaur, sauropod
25–28	Entu symbiote	Electrovore
29–32	Formian	Elemental, earth
33–36	Ghoran	Elemental, water
37–40	Goblin, space	Elmeshra
41–44	Hortus	Bodysnatcher slime
45–48	Ijtikri	Feeder fungus
49–52	Ilthisarian	Frujai colony
53–56	Jububnan	Herd Animal, marsh
57–60	Khizar	Ksarik
61–64	Mi-go	Moonflower
65–68	Osharu	Murzzilat
69–72	Pahtra	Predator, marsh
73–76	Raxilite	Scavenger slime
77–80	Scyphozoan	Swamp strider
81–84	Spathinae	Swarm corrovox
85–88	Telia	Tashtari
89–92	Vesk	Troll
93–96	Vilderaro	Vracinea
97–100	Wrikreechee	Writher swarm

Marsh Adventure Hooks

D20	Adventure Hook
1	Gases unknown to science bubble up through a marsh. Scientific institutions and mining corporations alike court adventurers to investigate this resource and its source—a difficult task because the gases cause local wildlife to become extremely aggressive.
2	A settlement was recently abandoned and flooded, its levies and drainage systems apparently torn down on purpose. The more explorers investigate, the more it seems the settlement’s former residents flooded their home to bury something terrible beneath the waters.
3	Drought has caused an otherwise permanent wetland to recede, uncovering hibernating amphibious eels that hungrily attack a nearby settlement whose residents are wholly unprepared for the previously slumbering threats.
4	For decades, local wetlands have filtered and absorbed techno‑magical waste from nearby factories, yet arcane pollution has reached critical mass, rapidly mutating flora. Carnivorous plants have grown to terrifying sizes, while other plants are growing lucrative, magic-infused fruits.
5	A planet’s millions of mangroves have always migrated, meandering several miles a year. Satellite imaging has identified a pattern to the movements, and in a few weeks, the mangroves and channels will have aligned to form Ibra’s holy symbol. What secrets might this confluence uncover?
6	Exploitation of a fen’s rare plants has inadvertently spread a deadly fungus, infecting several other worlds. The harvesting corporation desperately wants researchers to explore the locale to seek a remedy to the dangerous infecter.
7	Baffling yet consistent data has convinced surveyors that a massive marsh shouldn’t exist; it lacks the rivers or rainfall to remain wet, yet the area is consistently waterlogged. Magical consultants believe a connection to the Elemental Planes might be responsible.
8	A perpetual swamp, saturated with mystical otherworldly water, gradually saps its visitors’ memories. Explorers have returned from the marsh carrying strange, incomplete relics that might hold secrets to the Gap. Yet, the adventurers have no memory of how they found these artifacts.
9	“Itrion’s Tears” seemed a figurative name for a large marsh until the land recently peeled away to reveal a miles-wide staring eye, blinking away the swamp water. Locals desperately need someone to investigate and possibly negotiate with the eye. Is the entire world one living creature?
10	A vast bog’s rare flowers release psychotropic pollen on a 17-year cycle. The pollen infested nearby colonists, killing them in an ecstasy-fueled frenzy and caused them to rise as emotivores that even now attack their neighbors.
11	Ominous smoke began seeping from the bog as an errant and enraged fire elemental ignited an isolated peat deposit. It’s only a matter of time before the elemental seeks out a larger deposit that could set the continent ablaze.
12	Operating under the guise of ecologists, a cult of Oras has transformed a marsh into its personal laboratory. The cult’s experimental creatures have run amok, not only upending the local ecosystem but also threatening nearby settlements.
13	An estuary’s salinity increase has caused previously innocuous wildlife, such as clams and otters, to manifest magical abilities to adapt to these conditions. Their primal outbursts have begun to threaten nearby communities.
14	A proliferation of poisonous moss has grown so quickly that it’s dangerously changing the atmosphere’s composition. What is driving this explosive growth and what can stop it?
15	A fey monarch has offered extraordinary wealth in exchange for a talented starship crew’s services. Yet earning the payout involves tracking down the fey in a vast marsh. What’s so important that it warrants this trial and reward?
16	The threads of marsh-dwelling constellation moth cocoons encode secrets of distant star systems. This pristine silk is effectively a treasure map, yet local Xenowardens attack anyone who threatens the endangered moths.
17	An alien wetland isn’t damp from water; it’s semifluid due to ongoing radioactive and magical decay, creating a muddy expanse of irradiated ferns. The radioactive source has intensified in the past month. What does it portend?
18	Swamp-dwelling locals have gradually reshaped the land to expand their floating cities, yet this threatens ancient ruins that predate their culture. Xenoarchaeologists need help salvaging these sodden sites before they’re swallowed forever.
19	After sapient inhabitants hunted down most of the large predators in a swamp, those creatures’ prey have exploded in number and are swiftly reshaping the environment, threatening to flood local settlements.
20	A local bog has always been a haunt for criminals lying low, but a bandit leader has united these dissidents into a small army of raiders that has raided research stations and stolen dangerous biological agents. They’re now threatening to unleash these on innocent populations if not paid off.

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