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Nebulas are space environments occupying regions of vacuum and microgravity filled with tenuous but pervasive gas and dust. They can shine as colorful emission or reflection nebulae, blot out starlight as dark nebulae, or seethe with energized remnants of supernovae. For adventurers, they are natural lairs for space creatures, hidden pirate ports, and volatile regions where technology and magic alike can misbehave.
In rules terms, a nebula is an overlay on the standard Outer Space environment: it keeps vacuum, zero‑G, and radiation rules, then adds its own traits affecting visibility, sensing, and starship operations.
When a starship or similar vessel travels through a nebula, use the following simple framework in addition to your normal in‑system or interstellar travel rules.
For extended travel segments inside a nebula (hours or days):
At the start of each travel leg, the pilot attempts a Piloting check against an environment DC appropriate to the party’s level (usually simple or moderate DC from the GM Core difficulty table).
Degrees of Success (Travel Leg)
Critical Success: The ship makes excellent time. Reduce travel time for this leg (GM’s discretion; typically by 25%) and gain a +1 circumstance bonus on the next navigation check in this nebula.
Success: The ship stays on course; no special effect.
Failure: The ship drifts off the optimal path. Add a meaningful delay (such as 25% extra time for that leg) or have the ship emerge from the nebula slightly off the intended exit point.
Critical Failure: The ship blunders into a hazard—a radiation storm, debris pocket, or spatial anomaly (see Nebula Hazards, below)—and may also suffer a time delay.
During starship encounters set inside a nebula (tactical or cinematic):
Treat the nebula as an environmental effect that:
Imposes a flat check for certain Strikes or sensor‑dependent actions, similar to concealment.
Can be reduced or negated for the party if a science or magic officer spends an action each round to compensate (e.g., Calibrate Sensors, granting a circumstance bonus or removing the flat check for allies that turn).
The environment can also be written up as a threat or complication in a cinematic starship scene—e.g., a “Nebula Interference Field” that inflicts penalties or basic saves on all participants each round unless someone devotes actions to mitigating it.
Diffuse Obscurement: Dust and gas scatter and absorb light. Treat medium‑ or long‑range visual sight lines as having at least concealment (DC 5 flat check); in dense regions, increase this to greater concealment (DC 11 flat check) for targets beyond a short range band.
Localized Fog Banks: Clumps of denser material can create clouds equivalent to fog or smoke; within these areas, apply concealment to closer targets as appropriate.
Sensor Interference: Passive and active sensors that rely on EM signals—radar, lidar, many standard starship sensors—take a –1 circumstance penalty to checks to Detect, Identify, or Track targets in a nebula; in dense or ionized regions, increase this penalty to –2.
Range Attenuation: Long‑range scans and tight‑beam communications have their effective range halved within a nebula unless specifically designed for “cluttered space” operations.
Navigation Difficulty: Lack of clear star patterns, light scattering, and sensor noise make it easy to drift off course. Treat unguided travel in a nebula as navigationally confusing terrain, requiring periodic checks (see Navigation, below) to avoid delays or hazards.
Debris Pockets (Optional): Some nebulae contain higher‑density dust, comet shards, or wreckage; in such zones, treat the area like a loose asteroid field, with Piloting checks to avoid micro‑impacts or hull abrasion.
Nebulas are natural places to layer environmental or complex hazards on top of the base environment. Use standard hazard rules, but re‑skin effects for nebula flavor.
Ionized Gas Storm: Charged plasma flows or EM knots disrupt systems and occasionally lash ships with energy.
Dust & Micro‑Debris Fields: Dense clumps of dust, ice crystals, and rocky grains embedded in the gas.
Most exploration inside a nebula happens aboard starships, stations, or large structures, but EVA or “ship‑to‑ship” work is possible in localized areas like derelicts or gas mining platforms.
Use these adjustments when characters explore within a nebula:
Perception & Survival: Apply the same concealment and sensor penalties to Perception, Survival, and relevant exploration activities that depend on sight or scanning at distance. Finding hazards, tracking another ship’s ion trail, or visually navigating landmarks is harder.
Mapping & Getting Lost: Treat uncharted nebula sectors like trackless wilderness in 3D: failed navigation checks can cause groups to “miss” points of interest, loop through dead zones, or end up near unintended hazards.
Environmental Protections: Outside of a sealed structure, creatures still need full protection vs. vacuum, radiation, and possibly toxic or corrosive gas; armor’s environmental protections handle vacuum and basic radiation, but not all unusual gases.
Space‑adapted organisms—amoeboid plasmoids, energy feeders, or nebula dragons—use the gas and dust for camouflage and hunting.
Effects: Combine creature encounters with the existing concealment, sensor penalty, and movement complications to emphasize that the environment strongly favors native predators.
Nebulas excel as mixed‑mode challenges:
As backdrop complication in starship combat (flat checks, sensor penalties, and navigation tests).
As exploration space where mapping, environmental hazards, and weird physics are the main obstacles.
As cover and concealment for pirate bases, hidden research stations, or living megastructures.
Mechanically, everything here is built out of familiar tools—concealment, environmental hazards, radiation, and hazard/scene rules—so you can tune a nebula from “slightly spooky fog” to “star‑eating plasma labyrinth” without introducing bespoke subsystems.