Methane world

Methane world
Kraken Mare and Ligeia Mare, the methane seas of Titan, by the Cassini probe · NASA/JPL-Caltech/Space Science Institute, Public domain, Wikimedia Commons

Read off: Titan

An orange haze over dunes of hydrocarbon grains, rivers and lakes of liquid methane and ethane, and a sky that rains them slowly. The air is thicker than Earth's and mostly nitrogen, so a person needs no pressure suit, only warmth and oxygen: the cold here is far below anything on Earth. The light at noon is a dim twilight, and the gravity is so low that a person with wings strapped on could fly.

In figures

Gravity
0.14 g (Titan)
Day
Always the same face to its giant; one turn in 15.9 days
Air pressure
1.47 bar, about one and a half times Earth's
Air
95% nitrogen, 5% methane near the ground; no oxygen
Mean temperature
about −180 °C
Liquids
Lakes and seas of liquid methane and ethane; the largest is about three times the size of Ligeia Mare's 126,000 km²
Weather
Methane rain; equatorial dunes 1 to 2 km wide, some over 100 km long
Light
Dim
Going
Slow

Hear it

Hazards

  • Unbreathable air. There is air, but not air a human can live on: too thin, no oxygen, or the wrong gases. A mask and an oxygen supply are enough where the pressure holds; a full suit where it does not. D&D 5e: A creature holds its breath for 1 + its Constitution modifier minutes (at least 30 seconds), then gains 1 Exhaustion level at the end of each of its turns until it can breathe; it then loses all the Exhaustion it gained this way. Starfinder 2e: Thin atmosphere (GM Core): a few hours make a creature that is not acclimated fatigued; in severely thin air it attempts a Fortitude save every hour or becomes drained 1. With no oxygen at all, use holding breath and suffocating (Player Core). Armour environmental protections cover both. Archives of Nethys
  • Low gravity. Everything weighs a fraction of what it does on Earth: a person bounds rather than walks, falls slowly, and finds that stopping, turning and carrying momentum is harder than lifting. D&D 5e (House rule): House rule: jump distances are tripled, falling damage is halved, and a creature can lift and carry twice its usual weight. A creature unused to it has Disadvantage on Dexterity (Acrobatics) checks for its first day. Starfinder 2e: Low gravity (GM Core): Bulk is halved, so a creature carries twice as much and jumps twice as high and far; physical ranged attacks reach the 12th range increment. A fall deals nothing for the first 3 m (10 ft), then bludgeoning damage equal to a quarter of the rest of the distance. Archives of Nethys
  • Deep cold. Cold far below anything on Earth: steel turns brittle, rubber cracks and an unheated suit fails within hours. Heating and power are life. D&D 5e (House rule): House rule: a creature without heated protection makes a DC 15 Constitution saving throw at the end of each minute, taking 2d6 Cold damage and gaining 1 Exhaustion level on a failure. Cold resistance halves the damage but not the Exhaustion; Cold immunity passes automatically. Starfinder 2e: Incredible cold (GM Core, −62 °C / −80 °F or colder): fatigued after 2 hours of travel and moderate cold damage (4d6 to 6d6) every minute. A superior thermal capacitor protects against it. Archives of Nethys
  • Methane lakes. The lakes are liquid methane and ethane, far lighter than water: nothing human floats in them, and a boat must be built for them. A fall in means sinking, and the cold of the liquid is deadly at once. D&D 5e (House rule): House rule: a creature in the liquid sinks 9 m (30 ft) a round and cannot swim up without a Swim Speed or gear; it takes 4d6 Cold damage at the start of each of its turns unless its suit is heated. Starfinder 2e: Incredible cold (GM Core): moderate cold damage (4d6 to 6d6) every minute without a superior thermal capacitor; under the surface, holding breath and suffocating (Player Core) apply as well. Archives of Nethys

What may happen

  1. Methane rain falls in big slow drops, drifting down like snowflakes the size of marbles.
  2. A dry riverbed fills in minutes after a storm upstream, a dark flood carrying rounded pebbles of ice.
  3. For an hour the orange haze thins and the ringed giant shows through, pale and huge.
  4. The wind turns and the dunes of dark grains start to sing.
  5. A dark sea on the horizon lies flat as glass: the winds here are too gentle to raise more than ripples.
  6. A colonist goes by overhead on strapped-on wings, flapping in the thick air under the low gravity.
  7. A technician walks out in a heated suit and a breathing mask, no pressure helmet at all, and says it feels like freedom.
  8. A fine methane drizzle wets every visor all morning, beading and drying without ever quite stopping.
  9. At noon the light is a dim orange dusk. The solar panels barely tick over, and the base runs on its reactor.
  10. The dark grains of the dunes gum up a rover’s wheel bearings like wet sand.
  11. The survey boat crosses a methane sea, its wake spreading in slow, lazy ripples that take an age to fade.
  12. The rocks here are water ice, hard as granite in this cold. The geologist’s hammer rings on them like a bell.
  13. The thick cold air draws heat out of everything. A glove heater fails, and a hand goes numb within minutes.
  14. A battered probe rests on a plain of rounded ice pebbles, its parachute long gone: the first craft ever to land on this moon.
  15. A low fog of methane lies over the lakeshore and lifts so slowly that the party walks through it for hours.
  16. Jumping here is like jumping under water in slow motion: up through thick air, and a long gentle drift back down.
  17. On a dune crest two colonists run a flying school. The instructor, an old pilot named Marguerite, makes beginners hop for a day before they may flap.
  18. A dome on the horizon might be an ice volcano, the survey says. Nobody has ever seen it erupt.
  19. A tanker crew pumps liquid methane from the shore into insulated tanks bound for orbit. To them this sea is simply fuel.
  20. Sound carries well in the thick air: the crawler’s motor is heard long before it shows through the haze.
  21. The channels down the slope are dry and dark today. The forecast says the season of rain is years away.
  22. Waste heat from the base vents boils the methane out of the ground, and a small cloud hangs over the roof all day.
  23. A bright patch shows on the sea where there was none last week, then fades again. The scientists call it a magic island and cannot agree why.
  24. The long night begins: about eight Earth days of darkness, and the base switches to its night routine.
  25. The dunes run all one way, long straight ridges of dark grains that stretch beyond sight, some of them more than a hundred kilometres.

Adventure hooks

  1. A boat built for the methane seas was found drifting with its crew's suits aboard, empty and still sealed.
  2. The colony's flying racers bet everything on a course through the haze, and someone is sabotaging the wings.
  3. A chemist claims the dunes hold a molecule no lab can make, and wants guards for a month in the field.
  4. A flash flood buried the supply depot; digging it out of ice-pebble mud is a race against the next storm.

Who and what is met

Each is an SRD stat block under another name, as game masters reskin them.

Other worlds

Cold desert world, Ice moon with a hidden ocean, Hothouse world, Volcanic world, Airless world, Ocean world, Tidally locked world, Earthlike world, Acid world, Jungle world, Swamp world

Sources

This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at https://www.dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License, available at https://creativecommons.org/licenses/by/4.0/legalcode.

This product is licensed under the ORC License located at the Library of Congress at TX 9-307-067 and available online at various locations including paizo.com/orclicense, azoralaw.com/orclicense, and others. All warranties are disclaimed as set forth therein. Attribution: this rules layer is based on the following Licensed Material: Starfinder Player Core © 2025 Paizo Inc., Authors: Jessica Catalan, Thurston Hillman, Jenny Jarzabski, Mike Kimmel, and Dustin Knight; Starfinder GM Core © 2025 Paizo Inc., Authors: Jessica Catalan, Thurston Hillman, Jenny Jarzabski, Mike Kimmel, and Dustin Knight; Starfinder Alien Core © 2025 Paizo Inc. Authors: Kate Baker, Lau Bannenberg, Rigby Bendele, Vishesh Bhartiya, Joseph Blomquist, Jeremy Blum, Tineke Bolleman, Brent Bowser, Michael Bramnik, Patrick Brennan, Charlie Brooks, Jessica Catalan, Brite Cheney, Jeremy Corff, Caryn DiMarco, Anthony Dollinger, Steve Fidler, Kim Frandsen, Andrew D. Geels, Basheer Ghouse, Sen H.H.S., Katrina Hennessy, Thurston Hillman, Joan Hong, Jenny Jarzabski, Sara Jeffers, Mikko Kallio, Lysle Kapp, Mike Kimmel, Dustin Knight, Cole Kronewitter, Mahpiya, Letterio Mammoliti, Randal Meyer, Jacob W. Michaels, Matt Morris, Dennis Muldoon, Quinn Murphy, Elizabeth V Nold, Chesley Oxendine, Emily Parks, Glen Parnell, Randy Price, Kyle T. Raes, Jessica Redekop, Erin Roberts, James Rodehaver, David N. Ross, Pidj Sorensen, Joel Southall, Kendra Leigh Speedling, Drew Taylor, Sam W Tennyson, Jalen Todd, Ruvaid Virk, Viditya Voleti, Christopher Wasko, Nicholas Wasko, Jackson Wery, Shan Wolf, and Basil Wright. If you use our Licensed Material in your own published work, please credit us as follows: Biomes, Starfinder Second Edition rules layer © 2026 Michael Ghelfi. Reserved Material: the names of Biomes and its catalogues, its descriptions, sounds, art and code. Starfinder is a registered trademark of Paizo Inc.; this site is not published, endorsed, or specifically approved by Paizo Inc.

Open it in Biomes — MGS Toolbox