Special Terrain

Special terrain is atypical terrain that the expedition won’t encounter too often. Most campaigns will take place in worlds with standard atmospheres and normal gravity. This common terrain experience allows the players to use our little blue planet for reference.

Human man and woman in cockpit of spaceship experiencing zero gravity.

Hipsters in space.

Normal Gravity

Gravity is the attraction between two masses. The attraction gets stronger as the wates get greater, closer together, or both. EXP has a very simplistic system to accommodate for gravities other than our mundane terran 1G.

Familiarity with Encumbrance is essential for understanding the effects of Gravity

Gravity impacts every mechanical and biological process. Walking, flying, falling, and growth is dependent on gravity. An anthro persona expects her leg to have a certain wate stuck firmly to the planet’s surface. She also expects the foot she lifts into the air to come crashing back down to earth in a very predictable way. Flying animals and flying machines are dependent on the atmosphere being held firmly in place by gravity. For anyone who has fallen, the attractive force of the earth has been made painfully obvious.


Jumping is controlled falling. These jumping guidelines are for normal gravity with which we are familiar. A medium-sized persona can jump down two hexes down with little concern. If a persona chooses to leap four metres to the ground, she could make the two hex jump without misfortune.

Violently throwing the same persona four meters to the ground could lead to damage and injury. Under the influence of combat, impairment, or injuries, the referee may require a dexterity attribute roll.

Safe Landing Dexterity Roll
It’s not the fall that kills the persona it is the landing.

Target Roll

Hite (hexes)





































Fall only



Hite (hexes)




Target Roll

Hex adjustment by size. Tiny +2, Small +1, Large -1, Gigantic -2

If the player fails her persona’s safe landing dexterity roll, they take damage as if they fell the distance.


Falling is a failed jump. The persona may have voluntarily jumped into or involuntarily tossed into the gravity well. The persona will always get the chance to have a safe landing as if it were a jump. A failed jump inflicts damage during the sudden deceleration at the end of the fall.

Damage From Falling

HPS Damage = 1d6-1 per hex of hite

A 10 hex fall would inflict 0 to 50 HPS of damage on impact.

This calculation is for normal gravity falls. Heavier gravity would be worse, and lower gravity less worse. Any persona that can fly in any capacity will not take falling damage. Unconscious falling personas succumb to gravity even if they have the capacity for movement in the air.

Terminal Velocity

Terminal velocity is the fastest an object can fall in standard atmosphere and gravity. Terminal velocity is 55 h/u. It takes 78 hexes of free fall to reach terminal velocity. So there is no additional damage beyond 78 hexes of fall. A persona cannot take more than 390 HPS of damage on impact. Falling at terminal velocity would be a terminal event for most personas.

High Gravity

Personas experience high gravity due to planetary pull or massive acceleration. High gravity is any gravity between 1G and 3G. Beyond 3G personas cannot function. The 3G limitation includes aliens, anthros and robots.

The most common source of high gravity (HIG) is the increased surface gravity of an object with a great wate (typically a planet). The acceleration of a vehicle could create high gravity (typically a spaceship). Some of the more bizarre high gravity terrains arise from gravitational anomalies produced by gravity attacks from gravruptor grenades or gravity spills.

An increase in gravity will generally make things worse off for the personas. The high gravity will reduce their movement rates, their equipment will have a higher wate, and they will take more damage from falling.

Wate and HIG

The most significant impact on the persona is that they will be carrying extra wate. The wate of the persona and all her equipment increases under higher gravity. The persona’s wate increases regardless of diet and exercise. Gravity changes affect all equipment: pistols, armour, detectors, bandages, clothing, etc. These wate increases worsen the encumbrance of the persona The encumbrance load increases in higher gravity while carrying the same amount of equipment.

Additional Wate

additional wate = (Persona + Equipment Wate) * (G-1)

A 100 kg persona carrying 50 kg of equipment in 1.5G would add 75 kilograms to her encumbrance.

A persona with a wate of 75 kg in normal gravity would have a wate of 82.5 kilograms in 1.1G. The persona is carrying around an extra 7.5 kg of personal wate. A vehicle with a wate of 2000 kg in normal gravity has a wate of 2500 in 1.25G. The engine has to carry an invisible 500 kg payload.

Encumbrance Look Up Table
Don’t wait to calculate wate allowance. Rounded to nearest kg.

Encumbrance Level



























































































































































































Encumbrance Level

Movement and HIG

The additional wate of HIG acts like an encumbrance on movement. A 65 kg persona in 1.5G would increase by body wate by 32.5 kg. Her musculoskeletal system is designed to carry 65 kg. Her new high gravity wate is the same as carrying 32.5 kg of equipment. A persona with a 12 PSTR and a 32.5 kg load would be in the over-encumbered category.

Any equipment that the persona tries to carry would have its Wate increased by 50% as well. So even the lightest of objects may render the persona unable to move in HIG. This persona would be unable to move if she were in 1.7G. Her additional body wate would exceed her maximum wate allowance.

Encumbrance and Movement
Carrying stuff slows most personas down.




May Bolt.


May Run.


Normal move rate

Over Encumbered

Half move rate

Lift Only

No movement



Combat and HIG

HIG makes combat very challenging for personas that have a 1G upbringing. Encumbrance affects weapons impairing all attack rolls.

Range and HIG

Any projectile that has mass is affected by HIG. Gravity does not affect attacks that involve lazers, sonics, and fission. Attacks that involve bullets, arrows, rocks are affected by gravity. In addition to substantial attack roll penalties, the ranges of these weapons a reduced.

Gravity Range Double whammy

new decay = range * gravity

A weapon range of 100h and -10 decay in 2G would have a range of 50h and decay of -20.

Rules maintain game balance and assist creativity.
Do not let rules get in the way of the story or the fun.

For example, a crossbow has a range of 25 hexes with a penalty of -125 per hex beyond 25 hexes. In 2G, the crossbow would have a range of 13 hexes and a penalty of -250 per hex beyond 13 hexes. These penalties would be in addition to the Attack Roll Encumbrance Penalties.

Area of effect weapons have their area of effect reduced by high gravity. An AOE grenade with a six hex radius of effect would decrease to three hexes in 2G. Aerosols are unaffected by changes in gravity.

Performance Rolls and HIG

Performance Rolls are impacted based on the level of encumbrance the persona suffers. Performance Rolls for maneuvers unaffected by gravity suffer no penalty. Purely mental processes are affected the least. Highly dextrous processes are affected the most.

Encumbrance and Performance Rolls

Being encumbered makes it harder to do stuff.


DD Adjustment







Over Encumbered


Lift Only

Lift Only


DD Adjustment

Long Term Biological Effects

Personas can adapt to high gravities if exposed over a long time (months to years). There is no training effect if a persona is in the free, unencumbered, or encumbered categories. A persona’s PSTR may increase until it adapts to her new body wate.

Drawing of humanoid walrus sitting on ground wearing a dotted sash.

Adapted to gravity.

A 65 kg persona with a 12 PSTR is on a 1.5 g planet would be over-encumbered with the increase of her body wate. Her PSTR would increase until she was in the encumbered category when supporting her wate. This improvement will progress at the rate of 1 additional PSTR for every 12 months of uninterrupted high gravity. This persona could increase her PSTR from 12 to 16 with a four-year stay on a 1.5G world. The ref must note that the persona’s PSTR increase stops when the load of the persona’s increased body wate puts her in the encumbered category. The stay must be continuous, and any prolonged vacation from HIG will sacrifice PSTR gain for those 12 months.

The PSTR training only works for personas in the over-encumbered category. PSTR training does not work if the persona’s encumbrance is in the lift-only category. Personas overwhelmed by the high gravity cannot train their physical strength.

The ref can shorten the time needed for PSTR increases with special high gravity training clinics. The ref can also create barriers for personas that are abusing the benefits of high gravity training. There are no other attribute bonuses to be obtained by exposure to high gravity.

Extreme High Gravity

Extreme high gravity is lethal to personas used to a comfortable 1G. Gravity can become so high that the wate of a mammal’s chest cavity will expunge the air from her lungs, and she will suffocate. The essential fluids (blood, sap, oil) that move through the persona’s body can be brought to a halt by extreme gravities. Blood, sap, or whatever very high gravities will paralyze fluid that moves through the persona’s body.

Extreme Gravities
  • 3-4G movement rate is 0 h/u.

  • 5-7G fine motor skills impossible.

  • 8-10G difficult CON rolls to remain conscious

  • >10G damaging 1d6 per G per unit >10G

A persona trapped in a 12G gravity well will take 12d6 in damage every unit until squashed flat.

Low Gravity

Low gravity is any gravity less than 1G but at least significant enough to be considered present. An indicator of whether or not low gravity is zero gravity (ZOG) is whether a persona is in danger of achieving escape velocity by accident. An expedition may find low gravity (LOG) surroundings on small planets or asteroids. There are even some devices that develop anomalous low gravities. Low gravity is generally beneficial to the persona because it reduces the strains of Wate Allowance.

Wate and LOG

Low gravity offers the best wate reduction plan possible. Because wate is dependant on gravity, all items within a low gravity field have less wate than usual. A persona with a wate of 80 kg would have a wate of 40 kilograms in 0.5G. The persona is carrying 40 kg less than she usually has. The low gravity has the effect of making the persona appear even stronger because all equipment wates are reduced by 1/2 also. Vehicles would also miraculously have power for an additional amount of cargo. A 2000 kg vehicle would have the capacity for an extra 1000 kg of cargo on a 0.5G planet.

Wate Reduction in LOG

wate = (persona + equipment wate) * G

A 100 kg persona carrying 50 kg of equipment in 0.5G would add 75 kilograms to her wate allowance.

Movement in LOG

Low gravity doesn’t immediately yield faster movement rates. LOG does allow personas to move at the same speed they usually do with greater amounts of equipment. A persona with an 80 kg wate could add 40 kg to her wate allowance in 0.5G. An 80kg persona with a 12 PSTR carrying stuff in 0.5G would have a new WA would be 57 kg. Not only is her wate allowance greater, but the wate of the equipment she carries would be reduced by 1/2 in 0.5G. Players that are abusing this newfound wate allowance should face the challenges of equipment volumes.

The movement benefit of low gravity is in the reduced encumbrance effect on movement. A persona may be able to sprint in low gravity while carrying more stuff than she could in normal gravity. The usual encumbrance penalties apply in low gravity.

Combat in LOG

The changes in trajectories, wate of weapons, and body balance all affect LOG combat. Any changes to the parameters of one’s combat skills are not good. Type B attacks may fly further, but they don’t follow the same trajectory. Type A attacks don’t have the same crushing wate as before.

All these differences have an overall detriment on the Attack Roll. The penalties are not as dramatic as that of high gravity, but there are penalties all the same.

The bonus proficient (BP) of the persona decreases in proportion to the low gravity. For example, in 0.5G, the persona could use half her bonus proficient (BP). On a 0.25G planet, she could only use 1/4 her bonus proficient (BP) because the gravity is even less familiar. A persona with a BP of 142 can only add 71 to her attack roll when in 0.5G. Attack types A, B, and AOE, suffer the low gravity Bonus Proficient (BP) penalty. Attack types C, D, E, and F an unaffected by this penalty.

Range and LOG

The distance a ranged attack travels increases, but the effective range does not. Just because the projectile won’t fall to the planet’s surface any faster doesn’t make the weapon any more accurate. The accurate ranges of weapons do not change in low gravity, but the projectile will travel much farther than usual.

A small crossbow used in normal gravity has a range of 25 hexes and a penalty of minus 125 to hit per hex beyond 25. A small crossbow in 0.5G still has a range penalty of -125 per hex beyond 25 hexes. However, a bolt from this crossbow would have a range of 50 hexes and a decay of -63 per hex. The crossbow bolt will travel 66 hexes, but practical accuracy would not change. Not all weapons are affected by low gravity range increases. For instance, laser, sonic, ray guns, radiation, and stun weapons have no projectile to be affected by gravity.

Shrapnel area of effect weapons are unaffected by low gravity. The attack’s shrapnel will travel further, but it is only effective within its usual area of effect. For example, if the radius of a grenade’s effect is six hexes and used on a 0.5 g world, the shrapnel would travel twice as far, but the damage area would still be six hexes.

Performance Rolls and LOG

Low gravity does not affect performance rolls.

Low Gravity Sickness

Low gravity sickness is disabling nausea and balance disruption that incapacitates organic personas. Robots are unaffected by LOG sickness. There is a percentage chance equal to the gravity in a location that the persona will NOT suffer from low gravity sickness.

Chance of LOG Sickness

chance of sickness = 1 - Gravity

50% chance at 0.5G, and 75% chance at 0.25G.

To repel low gravity sickness, the player must win a tough MSTR attribute roll. A failed Mental Strength roll incapacitates the persona with nausea, unbalance and malaise. Low Gravity sickness lasts for 2 to 24 (2d12) hours. After which, the persona will spontaneously recover.

Long Term LOG Effects

The long-term effects of low gravity are hazardous to the persona. The lessened gravity will atrophy muscles, reducing PSTR, and dilute the blood, reducing CON. These effects take a long time to develop, and personas recover once back in normal gravity.

A persona can lose one point of PSTR for every two months of continuous stay in a low gravity environment. There is a percentage chance equal to the gravity that the persona will be unaffected and not suffer the loss of PSTR. For example, before a persona could be affected by a PSTR loss on a 0.9G planet, a 1d100 die roll would have to be higher than 90. The persona cannot lose more than half her PSTR attribute to lower gravity. PSTR can be regained at the rate of 1 point per month once in normal gravity. Veterinarians can combat the loss of PSTR with LOG exercise programs. The vet must make successive 5DD PT rolls for this training to be effective.

Lack of gravity affects the production of vital fluids, leading to a reduction in CON. The loss of CON is unstoppable and potentially lethal. A persona should roll vs gravity on 1d100 once a month of game time to determine if there is a loss of CON. If the persona rolls above the current gravity percentage, she will lose one CON that month. A persona can lose no more than three points of CON to low gravity. However, even this loss could kill personas with very low constitutions by reducing the attribute below one. Personas can regain the lost CON at a rate of 1 point for every 24 hours at full gravity.

No Gravity (ZOG)

No gravity is the absence of any significant gravitational attraction. No gravity is also known as zero-g, null g, or watelessness. The abbreviation chosen here is ZOG, for zero-G. An expedition will almost always encounter ZOG while in outer space. ZOG has detrimental long-term health effects identical to those of low gravity (LOG).

ZOG is fun for the expedition but a terror for the referee. The added complexity of 3d movement is challenging. ZOG is not just an extension of low gravity rules. There are additional complications involved in zero gravity.

Wate and ZOG

When gravity is absent, wate is absent also. In a ZOG environment, a persona can lift virtually anything. The problem becomes one of inertia as opposed to wate. Personas cannot send orbiting space stations into the atmosphere with a flex of their muscles. The question about pushing or lifting something in zero gravity is whether the object or the persona moves.

Movement and ZOG

It’s not that ZOG affects movement, but that in zero gravity, everything affects movement. Aside from the persona’s movement efforts, hits and attacks may also send the persona spinning. Normal walking doesn’t work in zero gravity. When the foot pushes off, it expects the body to come crashing back down to earth. Unfortunately, the forces generated by a single step sends the persona flying straight upwards.

Scrabble Grabble Movement

The easiest method of movement in ZOG is to pull one’s self from one handhold to another. The handholds may be protrusions in a corridor or natural handholds such as plants or rocks. The persona can pull herself along at 1/4 of her regular movement rate. When moving in this fashion, the persona cannot attack or do anything other than move.

Pushing Off Movement

Another movement method in zero gravity is pushing off an immobile object and flying along with the push’s momentum. The problem is that the persona will continue moving until she hits another solid surface, or friction from the atmosphere slows her down. Think of this movement like Newton’s first law: A body in motion remains in motion until an unbalanced force acts upon it. Once in motion, the persona will hurtle along at her regular movement rate. In the vacuum of space, this means that the persona may head off into oblivion. Zero gravity movement is easy but can be deadly for the unskilled.

The push method of movement works fine against massive objects. As the object’s wate becomes closer to the persona’s wate, the push becomes less effective. If the object is lighter than the persona, then the object will move away from the persona.

If a 100kg persona tries to push off from a 50kg object (possibly another persona), she will move at 50% of her movement rate. The object will move away in the opposite direction at 50% of her movement rate. Coordinating push-offs to optimize movement in ZOG can only be carried out by personas with skill in ZOG.

Combat and ZOG

In zero gravity, combat forces generate unintended movement. Punching a target may cause the target to fly away. Not all attacks generate movement forces. Weapons like lasers, sonic, radiation, ray, and stun weapons do not transfer momentum. Damage force converts into movement. Attacks will generate two types of motion: translational motion and rotational motion. Translational motion is straightforward to simulate. The target moves in a direction away from the attack.

Translational Motion from damage

move rate = 1 h/u per 10 HPS of Damage

A punch delivering 20 HPS in damage will send the target flying away at two h/u.

Translational motion in zero gravity is cumulative, and if a persona is flying away at 8 h/u and gets shot in the back (how callous) for 40 HPS of damage, she will now move at 12 h/u.

Rotational Motion from damage

The target may not just comfortably float away. There is a change that the movement will be chaotic and include undesired rotational motion. Rotational movement can be end over end, side to side, or a combination of both. Such spin may cause the spinning persona to suffer an attack of low gravity sickness.

Rotational Motion Sickness

chance = 1% per h/u

A persona spinning away at 12 h/u has a 12% chance of LOG sickness.

She will then have a 12% chance of getting sick from the rotational motion. Rotational motion sickness will incapacitate the persona for the remainder of the combat session.

Non-powered Attacks

Type A attacks (thrusting and striking) are very difficult to use in zero gravity. The forces required to do damage result in unintended rotational forces. The persona throws herself off-balance, trying to generate the damaging forces of thrusting and striking weapons. In zero gravity, this could result in rotational forces after every attack. For convenience and fun, EXP ignores the chaotic rotational forces.

However, translational forces take effect when the player wins an attack roll. If a motionless persona hits a motionless target, they will both fly away from each other. With 20 hit points of damage, the personas will move away from each other at two h/u. This system of resultant translational motion is accurate for personal combat amongst anthropomorphs of roughly equal size.

Type B attacks (non-powered projectile weapons) will not generate any translational or rotational motions for the attacker. However, the target will suffer one h/u of translational movement for every 10 HPS of damage.

Powered Attacks

Type C, D, E and F attacks are powered projectile weapons. Most guns generate significant translational motion for the firer. All guns will produce kickback in zero gravity unless stated explicitly in the weapon description. Skills like ZOG combat can negate these effects. Firer translational motion does not apply to laser, sonic, stun, ray, radiation, and other weapons which generate no projectile.

If a player rolls to hit with a bolt action rifle, her persona will move away from her target at one h/u per 10 HPS of possible damage. In zero gravity, the exploding bullet’s force converts into translational movement for the shooter. The target will move away at one h/u per 10 HPS of damage scored against her.

Grenades that generate projectiles or forces will also cause translational movement of targets. The targets will move away from the target hex (epicentre) at a rate of one h/u per 10 HPS of damage.

For example, an extra high-powered revolver inflicts 4 to 48 points of damage. When fired, the attacker will move away from the target at five h/u. If the target takes 12 HPS of damage, she moves in the opposite direction at one h/u.

Mechanical Effects and ZOG

ZOG can have drastic effects on mechanical equipment. Artifacts that depend on friction, levers, or balances may not function correctly in zero gravity. The malfunction does not mean nothing will happen, but that nothing expected will happen. A vehicle’s combustion engine can spin the wheels, but if the vehicle is floating 10 cm off the road, it will not move forward. The spinning tires may generate rotational forces causing some movement, but one can see how nothing expected would occur. The referee will have to improvise frequently in zero gravity.

Equipment designed for zero gravity, such as vac-suits, or spacer equipment, works in ZOG. Many mechanical devices have proven their worth in zero gravity: knives, golf clubs, pistols, pens, etc. ZOG function of an artifact is a discussion for the players and referee. These discussions can also result in the need for a Sphincter Roll.

Other ZOG Effects

The ZOG and LOG rules are the same in the following situations.

  • Ranges

  • Damage

  • Performance Rolls

  • Biologic Effects


This section is devoted to the differences in atmospheric pressure. This section does not cover toxic atmospheres and assumes that the atmosphere is potable. The strange atmosphere may from the life support system of a ship, the recycling unit of a vac-suit, or the natural atmosphere of a planet. The atmospheric pressure is our mundane terra of 1 Atmosphere.

Drawing of humanoid wearing safety suit in toxic environment.

Stylish and alive.

The atmosphere has both the correct chemical composition and the correct pressure for breathing. Any changes from 1 ATM will have detrimental effects on the persona. Lungs have a very restricted range in which they transfer oxygen into the blood (or carbon dioxide into the sap). Changes to the atmosphere, whether in composition or pressure, will have drastic effects on organics (anthros and aliens).

Changes in the atmosphere (ATM) usually result from exposure to very high altitudes or exposure to space vacuum. High ATMs usually occur on the surface of massive planets, which generally means that there is high gravity as well. The general principles of low ATM are easy to grasp: remove the atmosphere and die. Exposure to space will remove all atmosphere and kill the persona. Exposure to no atmosphere is often associated with zero gravity.


Persona land movement effects due to atmospheric changes are not significant. Aliens that fly cannot fly in any atmosphere density other than the one they evolved in.


Physical properties are unaffected by the quality of the atmosphere. Attack Rolls are unaffected, damages are identical, and ranges are the same regardless of the atmosphere in which combat occurs. Many type C attacks will not function in a vacuum because they depend on the atmosphere to operate.

Performance Rolls

Performance Rolls are unaffected unless a bulky spacesuit protects the persona. If the persona is protected, then the restrictiveness of the vac suit will hamper performance rolls. If the persona is not wearing a vac suit, then survival is more important than performance rolls.

High Atmospheric Pressure

High atmospheric pressure will cause increased wate on the persona because more gas is resting on the persona’s head. In a typical planetary atmosphere, a persona is supporting a column of air on her head. In 1.5 ATMs, an additional 225 kg of wate would be pressing down on the persona. Not only is the sheer force dangerous, but the change in pressure also affects the performance of the persona’s biology.

If the atmospheric pressure continued to increase, the persona’s eyes would push in, her lungs would collapse, and eventually, gas would force its way into the body through mucous membranes. The effect of the high atmosphere on personas is left for the referee to determine for her milieu. Essentially a high atmospheric pressure quickly crushes the persona, alien or robot to death.

Low Atmospheric Pressure

The effects of low atmospheric pressures separate into categories based on fractions of 1 ATM. The categories are hypoxia, dysbaria, anoxia, and ebullia. They represent progressively worse conditions of exposure to low ATM. These effects are cumulative and explosive decompression requires a persona to every category.

Normal (1 ATM to 0.70 ATM)

The standard atmosphere has no detrimental effects on personas.

Hypoxia (0.7 ATM to 0.41 ATM)

The partial pressure of the gases needed to get into the vital fluids (blood, sap, etc.) is too low. The system is having trouble exchanging the persona’s essential gases. Lungs can’t exchange oxygen into blood or CO2 into sap. When the tissues have an essential gas debt, lightheadedness will result.

Hypoxia Attack

A normal MSTR attribute roll is be required to avoid fainting when engaging in vigorous activity. Vigorous activity includes standing up too fast, running, or combat. A missed attribute roll will result in a swoon or blackout that lasts 1 to 20 units (1d20).

Dysbaria (0.40 ATM to 0.12 ATM)

In low-pressure, gases begin to expand as gases lacking pressure are wont to do. Dysbaria is the formation of undesired gas bubbles in the fluids and tissues of the persona.

Dysbaria can result in extreme discomfort, causing death. When subject to very low atmospheric pressure, organic beings are subject to a dysbaria attack. A dysbaria attack assaults the persona from the collection of nasty little gas bubbles inside her body. A dysbaria attack is activated whenever the pressure drops below 0.40 ATM. The attack happens once per exposure or additional drop in pressure. For example, a vehicle depressurizes to 0.30 ATMs exposes the personas to a dysbaria attack. If the vehicle depressurizes further to 0.20 ATM, the personas take another dysbaria attack.

Dysbaria Attack

A dysbaria attack hits like a 4d4 intensity toxin attack. The player must win a saving roll (versus constitution), or her persona takes full damage. If the player wins her saving roll, the persona takes 1/2 damage. For example, a persona exposed to 0.3 ATM pressure would suffer a dysbaria attack. The randomly generated attack (4d4) intensity is 10. Intensity 10 indicates 10d4 of damage. The referee rolls 27 hit points of damage. If the player wins the saving roll, her persona loses 14 HPS. If the player loses the saving roll, her persona loses 27 HPS.

Personas suffering a dysbaria attack also suffer a hypoxia attack.

Anoxia (0.12 ATM to 0.06 ATM)

Anoxia is the lethal advance of hypoxia. In this atmospheric category, there is no gas exchange at all, and life is not sustainable. Any organic persona exposed to this low atmospheric pressure is suffocating.

All organic personas suffer an immediate anoxia attack with this low level of atmospheric pressure. If the persona is suffering anoxia due to a drop in atmospheric pressure, a dysbaria attack is also required. If the persona is suffering anoxia due to immersion, there is no dysbaria attack.

Anoxia Attack (Suffocation)

The anoxia attack inflicts death and not damage. A suffocating persona will struggle to stay conscious. The player must win a normal MSTR attribute roll for her persona to remain conscious.

Once unconscious, the persona starts to die from whole body suffocation. Every organ that needs energy suffers damage. The persona’s body will die, and there is no saving roll offered. The only chance for survival is a timely rescue. The persona will be irretrievably dead at 1 minute per 4 points of CON.

If the persona does not lose consciousness, she can nominally function for one unit per point of constitution. Once the persona’s time has run out, she automatically goes unconscious and starts to die. For example, if a persona with an 11 CON manages to stay conscious, she will be able to struggle to safety for 11 units.

A persona with a 12 CON is in an airlock accident, rapidly reducing the atmospheric pressure to 0.1 ATM. The player wins her persona’s anoxia attack roll. The persona now has 12 units of consciousness. During this time, she tries to restore the airlock pressure. She cannot fix the malfunction within 12 units (about half a minute), and she goes unconscious. The expedition has 3 minutes to rescue her, or she is dead.

Ebullia (0.05 ATM to 0 ATM)

Ebullia results when the persona is subject to a total vacuum. Bodily fluids start roiling into a gaseous form as there is no pressure to keep them liquid. Body fluids vaporize and escape through the skin and respiratory structures. The body is low-temperature boiling. The ensuing ebullia attack is almost certain death.

Ebullia Attack

This attack is the rapid cold boil of essential liquids, which sounds fatal. For the most part, it is fatal. The player must win a normal MSTR roll to remain conscious. If successful, the persona can remain conscious for 1 unit per 4 points of CON. An unconscious persona can survive for 1 unit per point of CON. After this time, the persona is dead. Being exposed to a vacuum sucks.

A persona with a 12 CON is in an airlock accident, rapidly reducing the atmospheric pressure to zero. The player wins the ebullia attack roll. The persona will remain conscious for three units. During this time, she tries to get her safe suit on. She is unable to do so within three units, and she goes unconscious. The expedition has 12 units to rescue her, or she is dead.

Explosive Decompression

Explosive decompression is the instantaneous passing from a normal atmosphere to the extremities of space. Exatmo is the EXP term for the void of space, and it is short for "exterior to atmosphere." When a persona is exposed to exatmo instantly, she is as dead as being exposed to it slowly. The various attacks of decompression are purely faux science for role-playing fun. Below is the suggested approach for explosive decompression.

Explosive Decompression
  1. Hypoxia Attack

    1. Normal MSTR Roll vs unconsciousness

  2. Dysbaria Attack

    1. Con Roll vs 4d4 Intensity killing toxin attack.

  3. Anoxia Attack

    1. Normal MSTR Roll vs unconsciousness (yes, a second one)

    2. Death after CON/4 minutes

  4. Ebullia Attack

    1. Normal MSTR Roll vs unconsciousness (yes, a third one)

    2. Death after CON units

Extreme Cold

Outer space is cold. Exatmo is very, very cold. There is almost no heat energy in space atoms nearly stop agitating. Without a doubt, this is fatal to all lifeforms unprotected from exatmo.

EXP ignores the cryogenic damage from a temperature of nearly 0 Kelvin (-270 Celsius). The damage inflicted by dysbaria, anoxia and ebullia will eventually kill vacuum exposed life forms. The recovery of the body is that of a frozen solid body.

In the rare extreme cold situation within an atmosphere, the persona suffers an ebullia attack. In this case, the ebullia attack is from denaturating body tissues by crystallization instead of evaporation. Freezing tissue is as damaging as burning tissue.

Robot Effects

Reduced atmosphere and extreme cold are destructive to organic lifeforms. Inorganic personas, specifically robots, are less vulnerable but not immune to low atmospheric pressure. Unless the robot persona has exatmo hardening, low pressure may destroy her.

Robots are immune to the effects of hypoxia and anoxia. The robot does not go unconscious or lose hit points but does suffer damage. Any exposure to dysbaria or ebullia indicates a visit to the robot damage table. The robot takes an additional damage roll if the decompression is explosive. The player makes an additional roll on the robot damage table when she returns to normal atmosphere.

Robotic System Malfunction Location
What breaks when the robot breaks.

Die Roll (1d100)










Control Unit

All attributes.






Lose one.


Power Plant






Ref’s Own Table

Die Roll (1d100)



Robotic System Malfunction Severity
Severity of system malfunction.

Die Roll (1d6)





0 points



1 point



2 points

Die Roll (1d6)



A robot is in an airlock malfunction that results in explosive decompression. The pressure around the robot instantly drops to zero. The player makes four rolls on the robot damage table: one roll for dysbaria, one for ebullia, one for explosive decompression and one for cold ebullia. If these rolls do not destroy the robot, she can continue to function exatmo. There will be one additional damage roll when brought back into normal gravity.


Water applies to any fantastical liquid in which the personas find themselves immersed. Immersing a persona in liquid without a breathing apparatus will cause her to die from anoxia: aka drowning. If the persona is not in a drowning situation, the expedition can carry on adventuring underwater. Underwater terrain has movement restrictions, combat penalties, and other impairments. The deeper below the surface a persona is, the greater the water pressure she endures. Water pressure can crush equipment as well as personas.


The buoyancy of equipment is a wash. While equipment may have a lighter wate in water, it still creates drag. The equipment may have a decreased wate, but it still must be pulled through the water. For convenience, the drag counteracts any buoyancy benefits of the equipment. Adventures in liquids other than water require research by the referee regarding density and viscosity.


Underwater movement is slow and foreign. Some protective suit will restrict the persona. The drag of water is 1000 times greater than the drag of air. Usually, personas will sink to the bottom of whatever body of water they explore and walk along the immersed terrain. Terrain effects such as silt, kelp, and hills will deter the persona underwater just as sand, grass, and hills would on land.

Underwater combat movement is also impaired. Only personas with water-based movement types can benefit from the 3d movement that water allows. Only an alien with a water movement or an aquarian anthro can swim freely underwater. A robot can only sink unless it has locomotion that can operate underwater. Personal submersible devices may also allow the persona to move in a 3d fashion.

A persona walking through water can move at one h/u per 6 points of physical strength. Thus a persona with a 14 PSTR could push along at two h/u. The effects of wate allowance may keep a persona from moving at all. If the persona’s encumbrance is in the lift-only category, she can only sink. A persona can sink at a rate of 1 to 4 h/u, depending on the buoyancy of the equipment carried. A persona can safely sink off the edge of crevasses and float down at 1-4 h/u (1d4). Falling is not a concern, but increasing water pressure is a concern.


Swimming has two types. The first type is swimming to avoid drowning. The second type is swimming by aquatic life forms.

A non-aquatic alien or anthro cannot automatically swim. Untrained aliens or anthros swim not to drown. Swimming will allow the persona to move at 1/5 her on land movement rate. This movement rate will often be one h/u. Personas that have learned to swim can only use the 3d movement to avoid obstacles.

Aquarians can swim at the movement rate designated by their DEX. Some aliens have water locomotion and have a specific water movement rate. Only these personas can use the 3d advantage of the water.

Robots sink.

This detailed attention to movement underwater is for combat situations. Non-combat water movement is the same as any other non-combat movement.

Type A Attacks

Only thrusting Type A attacks work underwater. These weapons are tridents, spears, horns or hydraulic spikes. Unless the persona has underwater skills or has underwater evolved attacks, the player uses the bonus non-proficient. In most cases, the player cannot add the Damage Adjustment to the weapon damage.

Type B Attacks

Type B weapons are non-powered missile weapons such as axes, spears, bows, and objects. These weapons do not work underwater. The density of water offers too significant a drag for the weapon to be of any use. Aliens can use naturally evolved underwater type B attacks underwater.

Type C, D, E, F Attacks

Type C weapons are powered weapons such as guns, pistols, and rifles. Projectile firing weapons only have a range of a few hexes and have drastically reduced damage. Energy firing weapons do not work underwater unless specifically described to do so. Suggested penalties are -342 on the attack roll, range and damage reduced by ten times.

Naturally evolved underwater powered attacks will work.

Type AOE Attacks

Grenades work fine underwater. They just cannot be thrown any distance. A specialized underwater grenade launcher (torpedo) can deliver grenades. Aerosols do not work underwater unless described to do so.

Performance Rolls

Water has a dampening effect on maneuvers. Touch is hampered, vision is affected, and smell and taste are useless. The persona must also deal with equipment that wants to float away, sink, or dissolve. There is a +7DD penalty when attempting maneuvers underwater. Aquatic life forms (aquarian anthros and aquatic aliens) do not suffer this penalty.


If a persona immersed in water cannot swim, they are drowning. The immediate biological effect of water immersion at any depth is anoxia. Anoxia is the absence of the lungs' oxygen to transport into the blood (or the lack of carbon dioxide for the sap), and death quickly results. Underwater anoxia is also known as drowning.

A drowning persona will be unconscious within two units per point of constitution. Once unconscious, the persona will be dead within 1 minute (30 units) per 4 points of constitution. So a drowning persona with a 12 CON could struggle for 24 units and then would be dead 3 minutes later. There is no saving throw, and the persona is permanently dead.


None aquarian personas suffer an effective -3 on all attributes when underwater. This attribute penalty cannot kill the persona and cannot drop an attribute below zero.

Water Pressure

Water has wate. The deeper the persona goes, the more wate they are dealing with

Water Pressure and Personas
  • 5 hexes deep = 420 kg

  • 50 hexes deep = 4 tonnes

  • 500 hexes deep = 42 tonnes

  • Mundane Terra’s Titanic is resting at 2000 hexes deep

  • Mundane Terra’s Mariana Trench is 5000 hexes deep

A persona cannot venture below 25 hexes of water without pressure-protected gear. If personas still insist on going this deep, or if something else is insisting, they will suffer crushing damage. A persona suffers 1d4 damage per unit for every five hexes they are below the 25 hex limit. The pressures of deep water will certainly crush personas and equipment.

Under Pressure

damage per unit = 1d4 per (depth - 25 hexes)

At 30 hexes underwater, the persona will take 5d4 HPS every unit.


Quickly removing a persona from high pressure is extremely dangerous. The rapid change from high pressure to low pressure is similar to being exposed to low atmospheres. Rapidly depressurizing personas will suffer a dysbaria attack. Dysbaria is the formation of gaseous bubbles in the blood and tissues. A dysbaria attack requires the player to win a saving roll versus intensity 4 to 16 (4d4) toxin.

Mechanical Effects

Equipment hardened for EXATMO, underwater or high pressure is not damaged by water immersion. Whether water-hardened equipment works in water can depend on a Sphincter Roll. Any item with bespoke use or underwater purpose will work underwater.

Mechanical equipment that is not waterproof will takes damage in water. For more information of equipment damage, jump to Artifact Damage.


Fire is a special terrain that most personas know to avoid. These fire rules apply to combat fires, vehicle fires or trapped personas. Casually walking past a bonfire should not be a problem. Running through that bonfire will indicate fire damage.

These rules are not for weaponized fire attacks like a napalm grenade or a fusion gun. A successful fire attack will have specific rules of damage and burning. Fire in this section is for accidental fires that trap and surround the persona.

Don’t Let Fire Play With You
  1. Common Combustion

    1. 3d10 per unit

  2. Accelerated Combustion

    1. 6d10 per unit

  3. Immolation

    1. 1d10 units duration

    2. 2d10 per unit

Fire damages aliens, anthros and robots equally. Robots are not at risk of immolation post-exposure to fire.

Common Combustion

Common combustion is any flame arising from dry, fibrous material such as wood, paper, organic cloths or ropes. Every unit the persona is burning in common combustion, she takes 3-30 HPS (3d10) of thermal damage. A persona walking beside a bonfire does not take 3d10 HPS damage. A persona walking through a bonfire does take 3d10 HPS damage every unit in the fire.

Once the persona finishes playing with fire, there is a chance they will immolate. The percentage chance of catching on fire is equal to the damage rolled. The ongoing burning continues until the flames cease. Unchecked immolation will last 1-10 (1d10) units. Immolation inflicts an additional 2-20 HPS of damage (2d10) for every unit it continues to burn.

Accelerated Combustion

Accelerated combustion is any flame arising from fossil fuels, burning plastics, glowing blobs, or other flammable chemicals. Accelerated combustion indicates much higher energy and much more thermal injury. An accelerated fire will do 6-60 (6d10) HPS of thermal damage every unit the persona in the burning hex.

Once the persona finishes playing with fire, there is a chance they will immolate. The percentage chance of catching on fire is equal to the damage rolled. The ongoing burning continues until the flames cease. Unchecked immolation will last 1-10 (1d10) units. Immolation inflicts an additional 2-20 HPS of damage (2d10) for every unit it continues to burn.


Fire burns, smoke kills. Even if the persona avoids the fire, the smoke may still get her. Smoke will spread to where fire cannot get. For purely theatrical purposes, the referee may wish to delay the effects of smoke inhalation by some arbitrary number of units after the flames begin to rage in earnest.

Smoke plus an enclosed area may doom the persona even if she has successfully avoided getting burned. Smoke inhalation has the same effect as Anoxia, described above in (Low Atmosphere). Personas caught in any burning area where there is a finite supply of air will find themselves suffocating far faster than they burn, especially as the flames consume the air supply.