MSRD:Environment and Hazards

This material is published under the OGL 1.0a.

ENVIRONMENT & HAZARDS

Darkness and Light

It’s a rare mission that doesn’t end up in the dark somewhere, and heroes need a way to see. See Table: Light Sources for the radius that a light source illuminates and how long it lasts.

Table: Light Sources

Item	Light	Duration
Candle	5 feet	12 hours
Torch	20 feet	2 hours
Halogen lantern	40 feet	24 hours
Flashlight	20 feet*	6 hours
*Creates a beam 30 feet long and 5 feet high.

Heat and Cold

Heat and cold deal damage that cannot be recovered until the character counteracts or escapes the inclement temperature. As soon as the character suffers any damage from heat or cold, he or she is considered fatigued.

A character not properly equipped to counteract the heat or cold must attempt a Fortitude saving throw each hour (DC 15, +1 for each previous check). Failure means that the character loses 1d4 hit points. Heavy clothing or armor provides a –4 penalty on saves against heat but grants a +4 equipment bonus on saves against cold. A character who succeeds at a Survival check (DC 15) gains a +4 competence bonus on the save (see the Survival skill).

Searing heat or bitter cold (desert or arctic conditions) forces a character to make a Fortitude save every 10 minutes. Failure means that the character loses 1d6 hit points. Appropriate clothing and successful use of the Survival skill can modify the save, as noted above.

Catching on Fire

Heroes exposed to open flames might find their clothes, hair, or equipment on fire. Heroes at risk of catching fire are allowed a Reflex saving throw (DC 15) to avoid this fate. If a hero’s clothes or hair catch fire, he or she takes 1d6 points of damage immediately. In each subsequent round, the burning hero must make another Reflex saving throw. Failure means he or she takes another 1d6 points of damage that round. Success means that the fire has gone out. (That is, once the character succeeds at the saving throw, he or she is no longer on fire.)

A hero on fire may automatically extinguish the flames by jumping into enough water to douse him or herself. If no body of water is at hand, rolling on the ground or smothering the fire with blankets or the like permits the hero another save with a +4 bonus.

Starvation and Thirst

Sometimes heroes might find themselves without food and water. In normal climates, heroes need at least 1/2 gallon of fluids and about 1/4 pound of decent food per day to avoid the threat of starvation. In very hot climates, heroes need two or three times as much water to avoid dehydration.

A character can go without water for one day plus a number of hours equal to his or her Constitution score. After this, the character must make a Constitution check each hour (DC 10, +1 for each previous check) or take 1d6 points of damage.

A character can go without food for three days, in growing discomfort. After this, the character must make a Constitution check each day (DC 10, +1 for each previous check) or sustain 1d6 points of damage.

Damage from thirst or starvation cannot be recovered until the hero gets water or food, as needed. Even magical or psionic effects that restore hit points cannot heal this damage.

Suffocation and Drowning

A character in an airless environment (underwater, vacuum) can hold his or her breath for a number of rounds equal to his or her Constitution score. After this period of time, the character must make a Constitution check (DC 10) every round to continue holding his or her breath. Each round, the DC of the Constitution check increases by 1.

When the character fails one of these Constitution checks, he or she begins to suffocate or drown. In the next round, the character falls unconscious with 0 hit points. In the following round, the character drops to –1 hit points and is dying. In the third round after failing the check, the character dies of suffocation or drowning.

Smoke

Characters breathing heavy smoke or similar toxic gases must make a Constitution check (DC 10, +1 for each previous check) each round or spend that round choking and coughing. Characters who choke for 2 consecutive rounds take 1d6 points of damage.

Smoke also obscures vision, giving one-half concealment (20% miss chance) to characters within it.

Strangulation

When a character is strangled by an instrument or an attacker, use the rules below.

A character can strangle or choke a target of the same size category or one size category larger or smaller. The strangling attempt incurs an attack of opportunity.

To begin the choke, the attacker must succeed at an opposed grapple check. If the grapple succeeds, the attacker can choose to deal normal unarmed damage as well as choke the target. The target can hold his of her breath for a number of rounds equal to his or her Constitution score. After this period of time, the target must make a Constitution check (DC 10, +1 for each previous check) every round to continue holding his or her breath. The target begins to suffocate on a failed check (see Suffocation and Drowning).

If at any time the target breaks free or slips free of the grapple, the stranglehold is broken (although any damage that was dealt remains). Note that a grappled target who is not pinned can use his or her attack action to strangle his or her attacker.

Falling

A character takes 1d6 points of damage for every 10 feet of a fall, to a maximum of 20d6 points. If the character succeeds on a Reflex saving throw (DC 10, +1 for each 10 feet fallen), this damage is halved. If the saving throw fails, full damage is applied.

A character can make a Tumble check (DC 15) to treat a fall as if it were 10 feet shorter when determining the damage and Reflex saving throw DC required by the fall.

Falling Objects

Objects that fall upon characters (or creatures or vehicles) deal damage based on their size and the distance fallen, as noted on Table: Damage from Falling Objects.

Objects deal the initial damage given in Table: Damage from Falling Objects if they fall 10 feet or less. An object deals an additional 1d6 points of damage for every 10-foot increment it falls beyond the first (to a maximum of 20d6 points of damage). Objects of Fine size are too small to deal damage, regardless of the distance fallen.

A successful Reflex save indicates that the target takes half damage. The size of the falling object determines the save DC.

If the save fails by 10 or more, and the object is at least three size categories larger than the character, the character is pinned under the fallen object. A pinned character cannot move but is not helpless. The character can make a Strength check to lift the object off him or herself or an Escape Artist check (DC 20) to get out from underneath. The GM can modify the DCs for these checks based on the circumstances.

Table: Damage from Falling Objects

Object Size	Examples	Initial Damage	Reflex Save DC	Strength Check DC
Fine	Penny	0	n/a	n/a
Diminutive	Paperweight	1	0	n/a
Tiny	Wrench	1d3	5	n/a
Small	Vase	1d4	10	5
Medium-size	Briefcase	1d6	15	10
Large	Garbage can	2d6	20	20
Huge	Oil barrel	4d6	25	30
Gargantuan	Piano	8d6	30	40
Colossal	Vehicle	10d6	35	50

Poison

When a character takes damage from an attack with a poisoned weapon, touches an item smeared with contact poison, consumes a poisonous substance, inhales a poisonous gas, or is otherwise poisoned, the character must make a Fortitude saving throw. If the character fails, he or she takes the poison’s initial damage (usually ability damage). Even if the character succeeds, he or she typically faces secondary damage 1 minute later. This secondary damage also requires a Fortitude saving throw to avoid.

Poisons are detailed in the Craft(chemical) skill description.

Poisonous liquids are usually administered through injection or by application to a weapon. Poisonous gases must be inhaled to be effective. Poisonous solids are usually ingested with food or drink.

Perils of Using Poison

A character has a 5% chance (roll of 1 on 1d20) to expose him or herself to a poison whenever the character applies it to a weapon or otherwise readies it for use. Additionally, a character who rolls a 1 on an attack roll with a poisoned weapon must succeed at a Reflex saving throw (DC 15) or accidentally poison him or herself with the weapon.

Poison Immunity

Creatures with natural poison attacks are immune to their own poison. Nonliving creatures and creatures without metabolisms are immune to poison. Oozes and certain kinds of creatures are immune to poison, as detailed in their descriptions, though it is conceivable that a special poison could be synthesized specifically to harm them.

Disease

When a character is exposed to a treatable disease, the character must make an immediate Fortitude saving throw. The victim must make this roll when he or she comes into contact with an infectious carrier, touches an item smeared with diseased matter, consumes food or drink tainted with a disease, or suffers damage from a contaminated attack. If the character succeeds, the disease has no effect on him or her—the character’s immune system fights off the infection. If the character fails the save, he or she takes damage after an incubation period; once per day thereafter, the character must succeed at a Fortitude saving throw to avoid secondary damage. Two successful saving throws in a row indicate that the character has fought off the disease and recovers, taking no more damage.

The characteristics of some treatable diseases are summarized on Table: Diseases.

Type: The disease’s method of delivery—ingested, inhaled, or via an injury—and the DC needed to save. Some injury diseases can be transmitted by a wound as small as an insect bite. Most diseases that are inhaled can also be ingested (and vice versa).

Incubation Period: The amount of time before initial damage takes effect (if the victim fails his or her Fortitude save).

Initial Damage: The damage the victim takes after the incubation period.

Secondary Damage: The amount of damage the hero takes one day after taking initial damage, if he or she fails a second saving throw. This damage is taken each day the saving throw fails.

Table: Diseases

Disease	Type	Incubation Period	Initial Damage	Secondary Damage
Anthrax	Inhaled/Injury DC 16	1d2 days	1 Con	1d4 Con*
Small pox	Inhaled/Contact DC 15	2d4 days	1 Str and 1 Con	1d2 Str and 1d2 Con
Pneumonia	Inhaled DC 12	1d4 days	1 Str	1d3 Str and 1d3 Con
Hantavirus	Injury DC 14	1 day	1d2 Str	1d2 Str* and 1d2 Con*
Necrotizing faciitis	Contact DC 13	1d6 days	1 Con	1d3 Con*
West Nile virus	Injury DC 12	1d4 days	1 Dex and 1 Con	1d2 Dex and 1d2 Con*
Salmonellosis	Ingested DC 13	1 day	1 Str and 1 Dex	1 Str and 1d3 Dex
*If damage is sustained, make a second saving throw to avoid 1 point being permanently drained (instead of damaged).

Acid

Corrosive acids deal damage each round of exposure. The amount of damage varies depending on the acid’s strength, as noted on Table: Acid Damage.

Table: Acid Damage

Acid Strength	Splash Attack*	Total Immersion*
Mild	1d6	1d10
Potent	2d6	2d10
Concentrated	3d6	3d10
* Damage per round of exposure.

Acid damage from an attack reduces hit points. A character fully immersed in acid takes potentially more damage per round of exposure than a character splashed with acid.

The fumes from most acids are inhaled poisons. Those who come within 5 feet of a large body of acid must make a Fortitude save (DC 15) or take 1 point of temporary Constitution damage. A second save must succeed 1 minute later to avoid taking another 1d4 points of Constitution damage.

Electricity

Electrical hazards come in many forms, including stun guns, downed power lines, and electric security fences. Table: Electricity Damage gives damage values for various electrical hazards based on relative voltage. A character can make a Fortitude saving throw to reduce the damage by half. If that character is not grounded or is otherwise insulated from the current, a successful save indicates that no damage is suffered.

Table: Electricity Damage

Type	Examples	Damage	Fort DC
Jolt	Car battery, stun gun	1d3	10
Low voltage	Fuse box, electrical socket	2d6	15
Medium voltage	Industrial transformer, electric fence	4d6	15
High voltage	Power line, electric chair, lightning	8d6	20

SPACE ENVIRONMENTS

RADIATION SICKNESS

Radiation can be naturally or artificially produced. All stars produce radiation in some variety, and planets closer to these stars typically suffer more severe effects than worlds farther away. Many starships and other pieces of technology incorporate radioactive parts and fuel cells that can flood an area with harmful radiation when ruptured or exposed. Ancient alien civilizations might leave behind powerful artifacts that emit harmful radiation. Whether the source of the radiation is natural or artificial, any character in an environment rich with radiation may suffer some negative effects for exposure.

When characters are exposed to radiation, they may be afflicted with radiation sickness. Radiation sickness functions exactly like exposure to any other disease, following the normal rules for diseases. The Fortitude save DC and the effects of radiation sickness vary with the dose of radiation to which a creature is exposed.

Radiation exposure has five degrees: mild, low, moderate, high, and severe. To determine the degree of exposure, start with the type of exposure: either an irradiated area (such as the area near a nuclear explosion, after the fact, or a lab that has been flooded with radioactive gas), or a specific source of radiation (such as a lump of radioactive material). Then consult Table: Radiation Exposure to determine the degree of exposure based on the total time of exposure within a given 24-hour period (rounding up).

Table: Radiation Exposure

	————————— Time of Exposure (Minimum) ————————
Situation	1 round	1 minute	10 minutes	1 hour	1 day
Character in irradiated area:
Lightly irradiated	mild	mild	mild	mild	low
Moderately irradiated	mild	mild	low	low	moderate
Highly irradiated	low	low	moderate	moderate	high
Severely irradiated	moderate	moderate	high	high	severe
Character exposed to radiation source:
Lightly radioactive materials	mild	mild	low	low	low
Moderately radioactive materials	low	low	moderate	moderate	moderate
Highly radioactive materials	moderate	moderate	high	high	high
Severely radioactive materials	high	high	severe	severe	severe

The degree of the exposure determines the severity of the radiation sickness, as indicated on Table: Radiation Sickness. At low levels, radiation sickness is a slow disease. Often, a sick character suffers no severe short-term effects. This is reflected in the fact that even with a failed Fortitude save, the character might not suffer any Constitution loss.

Table: Radiation Sickness

Degree of Exposure	Fortitude Save DC	Incubation Period	Initial and Secondary Damage
Mild	12	1 day	1d4–2 Con*
Low	15	4d6 hours	1d6–2 Con*
Moderate	18	3d6 hours	1d6–1 Con*
High	21	2d6 hours	1d6 Con
Severe	24	1d6 hours	2d6 Con
* Minimum damage 0 Con.

TREATING RADIATION SICKNESS

Radiation sickness is considered a treatable disease that can be cured using the “treat disease” aspect of the Treat Injury skill. Treating radiation sickness requires a medical kit. Advanced medicine (such as neutrad) and advanced technology (including nanites and cybernetic implants) can also eliminate radiation sickness or obviate its harmful effects.

GRAVITY

The force that gravity exerts on a person determines how they develop physically as well as their ability to perform certain actions. In addition, gravity affects the amount of damage a character takes from falling. Gravity conditions may vary considerably from one environment to the next. For ease of play these rules present four simplified gravity environments: normal gravity (1.0 g), low gravity (<1.0 g), high gravity (>1.0 g), and zero gravity (0 g). The following sections summarize the game effects for each type of environment.

NORMAL GRAVITY

“Normal gravity” equates to gravity on Earth. Environments with normal gravity impose no special modifiers on a character’s ability scores, attack rolls, or skill checks. Likewise, normal gravity does not modify a creature’s speed, carrying capacity, or the amount of damage it takes from a fall.

LOW-GRAVITY ENVIRONMENTS

In a low-gravity environment, the pull of gravity is significantly less than what we experience living on Earth. Although an object’s mass doesn’t change, it becomes effectively lighter. This means that creatures bounce when they walk. It becomes easier to move and lift heavy objects as well as perform Strength-related tasks. In addition, creatures take less damage from falling.

Speed: A creature’s speed increases by +5 feet in a low-gravity environment. This bonus applies to all of the creature’s modes of movement.

Carrying Capacity: A creature’s normal carrying capacity is doubled in a low-gravity environment. In addition, the creature gains a +10 bonus on any Strength check made to lift or move a heavy unsecured object.

Skill Check Bonuses: Creatures in a low-gravity environment gain a +10 bonus on Strength-based skill checks (including Climb, Jump, and Swim checks).

Attack Roll Penalty: Creatures take a –2 penalty on attack rolls in a low-gravity environment unless they are native to that environment or have the Zero-G Training feat.

Damage from Falling: Creatures do not fall as quickly in a low-gravity environment as they do in a normal- or high-gravity environment. Falling damage is reduced from 1d6 points per 10 feet fallen to 1d4 points per 10 feet fallen.

Long-Term Effects: Long-term exposure to low-gravity conditions can cause serious problems when returning to normal gravity. A creature that spends 120 hours or more in a low-gravity environment takes 1d6 points of temporary Strength damage upon returning to normal gravity.

HIGH-GRAVITY ENVIRONMENTS

In a high-gravity environment, the pull of gravity is significantly greater than that which we experience living on Earth. Although an object’s mass doesn’t change, it becomes effectively heavier. It becomes harder to move and carry heavy objects as well as perform Strength-related tasks. In addition, creatures take more damage from falling. Even the simple task of walking or lifting one’s arms feels more laborious.

Speed: A creature’s speed decreases by –5 feet (to a minimum of 0 feet) in a high-gravity environment. This penalty applies to all of the creature’s modes of movement.

Carrying Capacity: A creature’s normal carrying capacity is halved in a high-gravity environment. In addition, the creature takes a –10 penalty on any Strength check made to lift or move a heavy unsecured object.

Skill Check Bonuses: Creatures in a high-gravity environment take a –10 penalty on Strength-based skill checks (including Climb, Jump, and Swim checks).

Attack Roll Penalty: Creatures take a –2 penalty on attack rolls in a high-gravity environment unless they are native to that environment.

Damage from Falling: Creatures fall more quickly in a high-gravity environment than they do in a normal- or low-gravity environment. Falling damage is increased from 1d6 points per 10 feet fallen to 1d8 points per 10 feet fallen.

Long-Term Effects: Long-term exposure to high-gravity conditions can cause serious problems when returning to normal gravity. A creature that spends 120 hours or more in a heavy-gravity environment takes 1d6 points of temporary Dexterity damage upon returning to normal gravity.

ZERO-GRAVITY ENVIRONMENTS

Creatures in a zero-gravity environment can move enormously heavy objects. As movement in zero gravity requires only the ability to grab onto or push away from larger objects, Climb and Jump checks no longer apply.

Most creatures find zero-gravity environments disorienting, taking penalties on their attack rolls and suffering the effects of Space Adaptation Syndrome (space sickness). In addition, creatures in zero gravity are easier to bull rush than in other gravity environments.

Space Adaptation Syndrome: A creature exposed to weightlessness must make a Fortitude save (DC 15) to avoid the effects of space sickness. Those who fail the save are shaken, and those who fail the save by 5 or more are also nauseated. The effects persist for 8 hours. A new save is required every 8 hours the creature remains in a zero-g environment. Creatures with the Zero-G Training feat do not suffer the effects of space sickness.

Speed: While in a zero-gravity environment, a creature gains a fly speed equal to its base land speed, or it retains its natural fly speed (whichever is greater). However, movement is limited to straight lines only; a creature can change course only by pushing away from larger objects (such as bulkheads).

Carrying Capacity: A creature’s normal carrying capacity increases by 10 times in a zero-gravity environment. In addition, the creature gains a +20 bonus on any Strength check made to lift or move a heavy unsecured object.

Attack Roll Penalty: Creatures take a –4 penalty on attack rolls and skill checks while operating in a zero-gravity environment unless they are native to that environment or have the Zero-G Training feat.

Modified Bull Rush Rules: A creature affected by a bull rush is pushed back 10 feet, plus 10 feet for every 5 points by which its opponent’s Strength check result exceeds its own.

Long-Term Effects: Long-term exposure to zero-gravity conditions can cause serious problems when returning to normal gravity. A creature that spends 120 hours or more in a zero-gravity environment takes 2d6 points of temporary Strength damage upon returning to normal gravity.

Weight vs. Mass

While an object in zero gravity loses weight, it does not lose mass or momentum. Thus, while a character could push a 10- ton piece of equipment around in space, albeit slowly, getting it to stop is a bit more difficult. If a character were to come between that piece of equipment and a solid object, that character would be crushed as if he were in full gravity—just more slowly.

For simplicity, assume that a Strength check to lift or move an object in zero gravity gains a +20 circumstance bonus. However, stopping an object already in motion does not receive this same bonus.

ATMOSPHERIC CONDITIONS

As with variants in gravity, a change in atmospheric conditions can cause major problems for characters. Unfortunately, not every planet will have the same atmospheric density or chemical composition as Earth, meaning that worlds otherwise hospitable to human life may not be ideal for humans born and raised on Earth.

Various atmospheric conditions (and their effects) are presented below.

CORROSIVE ATMOSPHERE

Some atmospheres (breathable or not) contain corrosive chemicals and gases. Corrosive atmospheres slowly eat away at foreign equipment and can cause significant equipment failure. The corrosion can be particularly troublesome in atmospheres that demand special survival gear, as any breach in a protective environmental suit renders it useless. Unprotected equipment exposed to a corrosive atmosphere takes 1d4 points of acid damage per hour of exposure. This damage ignores hardness and deals damage directly to the equipment, eating away at it slowly.

Creatures not wearing protective gear in a corrosive atmosphere take 1d4 points of acid damage per round of exposure.

THIN ATMOSPHERE

Planets with thin atmospheres have less oxygen per breath than the standard Earth atmosphere. Many thin atmospheres are the equivalent of being at a high elevation on Earth, such as on top of a mountain or in the upper atmosphere. A creature exposed to a thin atmosphere must succeed on a Fortitude save (DC 20) every hour. On the first failed save, the creature is fatigued. A fatigued creature that fails a subsequent save becomes exhausted for as long as it remains in the thin atmosphere. After 1 hour of complete, uninterrupted rest in a normal atmosphere, an exhausted creature becomes fatigued. After 8 hours of complete, uninterrupted rest, a fatigued creature is no longer fatigued.

THICK ATMOSPHERE

Thick atmospheres are those that contain a more dense concentration of certain elements, like nitrogen, oxygen, or even carbon dioxide, than the standard Earth atmosphere. These dense atmospheres sometimes contain a different balance of elements, while others simply contain a higher number of gas particles in each breath. The effects of exposure to a thick atmosphere are similar to those of a thin atmosphere (see Thin Atmosphere, above), except the Fortitude save DC is 15 instead of 20

TOXIC ATMOSPHERE

Some atmospheres (breathable or not) contain toxic gases that are debilitating or lethal to some or all forms of life. The atmosphere is treated as always containing a type of inhaled poison.

VACUUM

Despite some popular myths, moving into a vacuum does not cause the body to explosively decompress, nor does it cause instant freezing as heat bleeds away from the body. Rather, the primary hazards of surviving in the vacuum of space are the lack of air and exposure to unfiltered ionizing radiation.

On the third round of exposure to vacuum, a creature must succeed on a Constitution check (DC 20) each round or suffer from aeroembolism (“the bends”). A creature that fails the save experiences excruciating pain as small air bubbles form in its bloodstream; such a creature is considered stunned and remains so until returned to normal atmospheric pressure. A creature that fails the Constitution check by 5 or more falls unconscious.

The real danger of vacuum comes from suffocation, though holding one’s breath in vacuum damages the lungs. A character who attempts to hold his breath must make a Constitution check (DC 15) every round; the DC increases by 1 each round, and on a successful check the character takes 1 point of Constitution damage (from the pressure on the linings of his lungs). If the check fails, or when the character simply stops holding his breath, he begins to suffocate. In the next round, he falls unconscious with 0 hit points. The following round, he drops to –1 hit points. On the third round, he drops to –10 hit points and dies.

Unfiltered radiation bombards any character trapped in the vacuum of space without protective gear. A creature exposed to this ionizing radiation suffers from severe sunburn as well as the effects of radiation exposure; the degree of exposure depends on the nearest star’s classification (see Star Systems below for more information).

DECOMPRESSION

The sudden decompression of a starship, vehicle, or other object can be dangerous to creatures inside. Whenever a sealed environment within a vacuum is breached, all of the air inside rushes out quickly to equalize the air pressure. Creatures within the decompressing environment must succeed on a Reflex save (DC 15) or be thrust toward the breach (and possibly beyond it) at a speed of 60 feet per round. Creatures that are three size categories larger than the breach’s size category are big enough not to get dragged toward the breach (no Reflex save required). For example, a Fine breach pulls only Fine, Diminutive, and Tiny creatures toward it; creatures of Small size or larger are unaffected.

If the breach’s size category is larger than the creature’s size category, the creature passes through the opening and is blown out into the vacuum. If the breach’s size category is the same as the creature’s size category, the creature is blown out into the vacuum and takes 1d6 points of damage as it gets pushed through the breach. If the breach is one or two size categories smaller than the creature’s size category, the creature isn’t thrust into the vacuum but takes 2d6 points of damage as it slams against the area around the breach. It takes another 2d6 points of damage each round until the air completely evacuates from the decompressed compartment or until the creature pulls itself away from the breach with a successful Strength check (DC 20).

The time it takes for all of the air to evacuate from a compartment depends on the size of the breach and the volume of the decompressing compartment, as shown in Table: Decompression Times.

Once the air has completely rushed out through the breach, the pressure equalizes and the interior environment becomes a vacuum.

Table: Decompression Times

Breach Size	Decompression Time
Fine (1-inch square)	3 rounds per 10-foot cube of air
Diminutive (3-inch square)	3 rounds per 10-foot cube of air
Tiny (6-inch square)	2 rounds per 10-foot cube of air
Small (1-foot square)	2 rounds per 10-foot cube of air
Medium (2 1/2-foot square)	1 round per 10-foot cube of air
Large (5-foot square)	1 round per 10-foot cube of air
Huge (10-foot square)	1 round per 20-foot cube of air
Gargantuan (15-foot square)	1 round per 30-foot cube of air
Colossal (20-foot square)	1 round per 40-foot cube of air

STAR SYSTEMS

A star system can contain one star or multiple stars. Humans are more likely to find habitable planets in systems with single stars. In reality, more than half of all star systems have two or more stars, and these systems typically contain planets that are inhospitable to human life.

STAR TYPE

Stars are classified using a lettering system that describes the star and gives information about its type. Known as the spectral class of a star, a designation of O, B, A, F, G, K, or M is given to the star based on its mass and energy output. Class O stars are the hottest, largest, and brightest stars, and class M stars as the smallest and coldest, with a gradual scale between them. Since a star’s mass determines how hot it burns (as well as how strong its gravity pull is), the star’s classification actually helps extrapolate the kinds of planets that might be in that star’s system. Since larger stars burn hotter and smaller stars burn cooler, the mass of a star determines the climate of the worlds that orbit it.

In addition to the standard array of star types, several other types of stars (or what were once stars) might be found at the center of a star system. Most of these stars (called “non-main sequence stars”) have characteristics that make certain planetary conditions impossible, and no type of non-main sequence star is likely to support worlds hospitable to human life. Types of non-main sequence stars include black holes, neutron stars, white dwarf stars, black dwarf stars, brown dwarf stars, and red supergiants.

Degree of Ionizing Radiation: Ionizing radiation—radiation that breaks down atoms within living tissue—is common in space. All stars produce and emit harmful levels of ionizing radiation, and a star system is considered an “irradiated area” for the purposes of determining radiation exposure, particularly in the vacuum of space. (Planetary atmospheres and protective environment suits can protect a creature from ionizing radiation.) The degree of radiation exposure depends on the nearest star’s classification, as shown in Table: Star Systems. For systems with two or more stars, increase the degree of radiation by one grade (lightly becomes moderately, moderately becomes highly, and highly becomes severely).

Number of Planets: The number of planets in a given star system can be determined by rolling on Table: Star Systems. For systems with multiple stars, use the star with the fewest planets allowable to determine the number of planets in the system.

HOSPITABLE STARS

The chief classifications of hospitable stars are F, G, and K. These stars produce the right amounts of heat and the right types of radiation to allow human-compatible worlds to exist. Not every world around a Class F, G, or K star is hospitable; however, even inhospitable worlds within such systems could be made to support human life with artificial modifications to their ecosystems (a long a painstaking process called “terraforming”).

INHOSPITABLE STARS

Class O, B, A, and M stars are the least likely to support planets capable of hosting human life. T he s tars toward the hotter end of the spectrum simply produce too much heat to allow living, breathing organisms to thrive. Class M stars do not give off enough heat to support life at the distance Earth orbits its sun, and these stars are also known to be violently unstable and prone to bursts of stellar activity.

Table: Star Systems

Star’s System’s Classification	Degree of Ionizing Radiation1	Number of Planets
Class O (blue-white)	Highly irradiated	1d4+1
Class B (blue-white)	Moderately irradiated	1d4+2
Class A (blue)	Moderately irradiated	1d6+2
Class F (green)	Lightly irradiated	1d6+3
Class G (yellow)	Lightly irradiated	1d6+4
Class K (orange)	Moderately irradiated	1d6+5
Class M (red)	Highly irradiated	1d8+2
Non-Main Sequence Star’s Classification	System’s Degree of Ionizing Radiation1	Number of Planets
Black hole	Highly irradiated	—
Neutron star	Severely irradiated	1d4–1
White dwarf	Moderately irradiated	1d4+1
Black dwarf	Lightly irradiated	1d4+2
Brown dwarf	Lightly irradiated	1d4+1
Red supergiant	Highly irradiated	1d4–1
* See Table: Radiation Exposure for details.

BLACK HOLES

Black holes are stars that have expended their fuel sources and exploded in a massive supernova. Few, if any, planetary bodies survive the initial death of such a star. Once the star has exploded, its gravity is so great that it collapses in on itself and warps light, time, and space around it. Black holes drag all nearby matter into its center, collecting rings of cosmic debris called accretion discs that can be seen at great distances. Some planets and asteroids might survive being pulled into a black hole long enough for some adventuring, but they are incredibly dangerous places to explore.

NEUTRON STARS

A neutron star is a large star that has exhausted its fuel source but hasn’t collapsed in on itself. Instead, the entire star’s remaining matter compresses into a much smaller body mere kilometers in diameter. Within this tightly packed core, the star’s density crushes the atoms into an object composed entirely of subatomic particles known as neutrons. Planets orbiting a neutron star are typically cold, lifeless, and severely irradiated. Another type of neutron star is the pulsar, which emits severe levels of radiation at great distances.

WHITE DWARF STARS

A white dwarf star is so much smaller than a neutron star that it does not have the mass to collapse in on itself. Instead, white dwarfs are typically small and dense and surrounded by rings of wreckage that were once planetary bodies in its system. White dwarfs emit little light or energy, and the rings surrounding them are usually cold and dark. However, these rings are not bombarded by as high levels of radiation as in a neutron star and could potentially support life, assuming enough heat could be generated.

BLACK DWARF STARS

Black dwarf stars completely burn out after expending their fuel. Truly the most stable of dead stars, b lack dwarfs simply consume their fuel supply and then cool into a cinder that emits no light or heat. Any planetary systems that existed around a black dwarf will remain intact; however, they usually become barren and frozen once their heat and light source is gone.

BROWN DWARF STARS

In many ways, the brown dwarf is not even a star. Brown dwarf stars are stellar bodies that almost coalesced into true stars but never managed to form completely. Brown dwarfs are dim and small. They may have planets in their system, but rarely can these worlds support life due to the lack of heat or light.

RED SUPERGIANTS

Most red supergiants begin their lives as average-sized stars. However, they burn hot and expend their hydrogen fuel supplies quickly. When its hydrogen supply is depleted, a red supergiant begins burning other, heavier elements such as helium, causing the star to expand to enormous size. An expanding red supergiant consumes its innermost planets and then burns so hot and bright that it renders all other planets in its system incapable of supporting life naturally.

STELLAR HAZARDS

Two types of stellar hazards can create higher-than-normal levels of ionizing radiation: solar flares and cosmic rays.

SOLAR FLARES

Solar flares release tremendous amounts of electromagnetic energy (including harmful ultraviolet rays and X-rays), as well as highly charged protons and electrons. The effects are comparable to a radioactive blast from one hundred million billion tons of TNT (compared to the 20,000-ton equivalent blasts that destroyed Hiroshima and Nagasaki). Fortunately, while solar flares aren’t rare, they are predictable.

An unprotected creature exposed to radiation from a solar flare is treated as “severely irradiated” for the purposes of determining the radiation’s effects (see Table: Radiation Exposure).

COSMIC RAYS

Cosmic rays, unlike solar flares, cannot be predicted. Consisting of subatomic particles moving at relativistic speeds, these rays can penetrate miles of solid mass (though extremely few get through the Earth’s atmosphere without colliding with other atoms or molecules, effectively rendering them harmless). In space, these subatomic particles can cause severe cell damage, even genetic mutation.

An unprotected creature exposed to radiation from a cosmic ray shower is treated as “highly irradiated” for the purposes of determining the radiation’s effects (see Table: Radiation Exposure).

XENOBIOLOGICAL HAZARDS

In addition to facing dangerous creatures and harsh environmental conditions, space explorers must occasionally contend with xenobiological hazards—nonsentient forms of life that are, by their verynature, menacing and dangerous without being openly adversarial.

Xenobiological hazards are treated more like traps than creatures. They have Challenge Ratings (CRs), and heroes earn experience points for surviving or overcoming them. A xenobiological hazard might be a pool of corrosive slime or a patch of mold that feeds on the warmth of nearby life forms. It’s not deliberately predatory, just dangerous by nature.

Two kinds of xenobiological hazards are described here.

ENDOTHERMIC MOLD (CR 2)

Endothermic mold feeds on warmth, siphoning heat from anything around it. A patch of endothermic mold is red-brown in color and 5 feet in diameter, and the temperature is always cold in a 30- foot radius around it. Living creatures within 5 feet take 3d6 points of nonlethal cold damage. Fire brought within 5 feet of the mold causes it to instantly double in size.

A 5-foot patch of endothermic mold is destroyed if it takes 5 or more points of cold damage.

SPACE SLIME (CR 4)

This sticky, translucent green slime devours flesh and organic materials on contact. Wet and sticky, it clings to walls, ceilings, and floors in patches, growing and spreading as it consumes organic matter. It drops from walls and ceilings when it detects movement (and possible food) below.

A single 5-foot square of space slime deals 1d6 points of Constitution damage per round while it devours flesh. On the first round of contact, the slime can be scraped off a creature (most likely destroying the scraping device), but after that it must be frozen, burned, or cut away (dealing damage to the victim as well). Against wood or metal, space slime deals 2d6 points of damage per round, ignoring metal’s hardness but not that of wood. It does not harm stone. An injection of sporekill or 10 or more points of cold or fire damage destroys a 5-foot patch of space slime.

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