Chapter 19: Special Terrain

Special terrain is weird terrain that the expedition won’t encounter too often. Most campaigns will take place in worlds with normal atmospheres, and normal gravity where the players, and the referee, can use the reference of our little blue planet. 

The terrain effects discussed in this chapter are ones that affect the entire environment of the expedition. How these terrains affect role-playing systems like combat, movement and wate are discussed. A bit of basic exo-physiology is included for good measure, or confusion. The biological effects of high, low and zero gravity are included so that the referee can extrapolate for those situations that are not covered in this chapter. The effects of dense and light atmospheres, and liquid environments are discussed also. Terrains that the referee must construct on her own, preferably from other EXP systems, are poisonous ones, or ones with constant meteorological effects like wind, rain or snow.

studiostoks illustration. desat HM

Gravity Effects

Very briefly, gravity is the attraction between two masses. In EXP they are called wates. The attraction gets stronger as the wates get greater, closer together, or both. Gravity is so important that no mechanical or biological process can exist without taking gravity into account.

Walking, flying, falling, and growth are all affected equally by gravity. A walking human 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 dependant 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.

Gravity is an ever pervasive element, and its total effects in a role-playing game cannot be overemphasized, What the gravity altering referee must remember is that every aspect of this game has been based on a 1G (one gravity) world. If you were to change the gravity of a scenario, every wate would be changed, every weapon range would be altered, every fuel consumption would be changed, every persona’s movement rate would be altered, and long term biological and mechanical effects would have to be taken into account. Such obstacles should not deter any referee with a calculator and an imaginative mind. Alternate gravities can be riotous fun, and the following paragraphs are devoted to them.  What will be covered are the effects with high gravity (greater than 1G), low gravity (less than 1G), and no gravity (less than .1G).


EXP constantly has terrible destructive forces being hurled about indiscriminately, however falling is a still a good old fashioned way to get killed. Among the more traditional perils of adventuring is the favoured “step on the rotten plank bridge three hundred feet above the jagged rocks and crashing waves.” The mortal consequence of such a mishap, and failed DEX roll, is hardly in doubt.

Voluntary: In short a persona can safely jump 2 hexes downwards without any concern. For somewhat more manageable heights on a 1G world, say two hexes, there might be some question about how well the typical persona would fare. If your persona chooses to leap four metres to the ground, has good ankle support and manages to avoid landing on her head, she could make a 2 hex jump without misfortune. If, however, that same persona finds herself shoved out of a four metre-tall tree (2 hexes), has no clue what she’s going to land on, hitting every branch on the way down she can expect to take some damage she may expect to wake up several hours later, if ever.

Table 19.1: Safe Landing, indicates a degree of difficulty for a jumping DEX roll depending on the height and landing surface. Merc Ades, with a DEX of 14, leaps from a third story balcony onto a fig stand below. It’s an apartment building so we assume 3 metres per floor: Merc is dropping 2 hexes onto a surface that’s plenty pliant, but not particularly smooth or flat) Merc Ades needs not make any roll and lands safely  amongst the figs. If the landing is complex due to the surface, a change in gravity, being thrown or tossed the nature of the surface becomes more complex and makes the change of landing safely more difficult. 

Table 19.1 Safe Landing

It's not the fall that kills the persona it is the landing.
Height (hexes)SafeNormalComplex
<1----Easy (1d10)
1-2 --EasyNormal (1d20)
2-3Normal (1d20)HardTough

Involuntary: If a persona is thrown, or unexpectedly succumbs to gravity  she could easily be damaged by a 2 hex (4 meter) fall. If the above persona Merc Ade were thrown from the balcony she would need to make a successful DEX attribute roll to avoid getting damaged. Merc Ades lands flat on her back, squashing several kgs of figs. Since she fell 3 hexes, she takes 3d6 – 3. By a complete fluke, she rolls two 1s and a 3, which gives a grand total of 2 points. She shakes off the effects and sprints away down the street.

Damage by falling, as any skydiver will blackly attest to, results from the sudden deceleration not the fall. In EXP terms, this means that damage from hitting a hard surface at high speed comes in neat little packages of (d6-1) for every hex fallen. Those of you readers well-versed in basic physics may be sputtering at this stage, since falling objects accelerate and thus should suffer varying damage rates depending on time. We just do not have the resources for such a factor.

Damage from Falling = 1d6 -1 per hex of height

Subtracting one point from the damage roll serves to simulate the effects of short drops, where it is entirely possible that by landing spread-eagled on the ground, your persona will completely avoid injury. Needless to say, falling uncontrollably onto a soft surface is preferable to falling uncontrollably onto a hard surface. However, the distinction between the two becomes blurred for high enough falls. Hence, falling ten feet into water beats falling ten feet onto asphalt…but from a mile up? To reflect this, the referee will want to mitigate the damage of hitting a pile of mattresses by some fixed value that will be very meaningful for a few dice of damage, and utterly irrelevant for a dozen.

Terminal Velocity: Terminal velocity is not just terminal for a persona. It is the fastest an object can fall in 1G normal atmosphere environment. Terminal velocity for an anthropomorph is 55 h/u, it takes 78 hexes of free fall to reach terminal velocity. So terminal velocity is terminal when the persona catastrophically decelerates for 78d6-78 hit points of damage. 

Delicately adapted to slightly increased gravity.
Delicately adapted to slightly increased gravity.

High Gravity

How can personas find themselves in a situation of high gravity? The most common sources of high gravity (HIG) are either the high surface gravity of an object with a great wate (typically a planet), or the acceleration of a vehicle  over a long period of time (primarily a spaceship). Some of the more bizarre high gravity situations can arise from gravitational anomalies produced by gravruptor grenades or gravity spills. An increase in gravity will generally make things worse off for the personas. Their movement rates will be reduced, their equipment will have a higher wate, and they will take more damage from falling.

Extreme High Gravity:  The biological limits of reasonably high gravities are determined mostly by effect of body wate on encumbrance. Extreme high gravity is lethal to personas used to a comfortable 1G. The following subsection are examples of how moderate HIG (1-2G) affects the persona.  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. Blood, sap, or whatever fluid that moves through the persona’s body, will be paralysed by very high gravities. Considering all such fluids to be similar in density and consistency the effects of very high gravity can be applied equally to all organic personas.

At 3-4G no movement is possible. At 5-7G the accuracy of simple finger movements will  suffer a penalty of at least -800 to hit a target. At 8-10G, impossible CON attribute rolls would be required to remain conscious (completely immobile, but conscious). Any gravity greater than 10G will be lethal to the persona. Gravities higher than 10G can be survived provided the exposure is less than a unit. For every unit of exposure to gravity above 10, the persona will take one d6 per G . So a persona trapped in a 12 g gravity well will take 12d6 in damage every unit until squashed flat.

Wate: In higher gravity the persona’s wate will increase regardless of diet and exercise. A persona with a wate of 75 kg in 1 gravity (1G), would have a wate of 82.5 kg in 1.1G. This means that the persona is carrying around an extra 7.5 kg of personal wate. The effect is worse for very large objects, a vehicle with a wate of 2000 kg in 1G, would have a wate of 2500 in 1.25G. This is the same as the engine having to deal with an invisible 500 kg payload. The ref must remember gravity changes  effect all equipment: pistols, armour, detectors, bandages, clothing, etc.

Movement: The wate added to the persona by the increased gravity is the greatest threat to her movement rate. The intrinsic increase in her wate due to a gravity increase counts as encumbrance.  Personas with high PSTRs will function more easily than weak over-wate personas in HIG. This system is easily managed for long term steady state gravity situations, but can become cumbersome with quickly changing gravities.

If a 65 kg persona, with a 12 PSTR, were to subjected to 1.5G she would face the following problems. Her body wate would increase by 32.5 kg, but her musculo-skeletal system is still only designed to carry 65 kg. Her added wate is the same as carrying 32.5 kg of equipment, although evenly distributed. Using Table 18.1: Wate Allowance and Encumbrance  shows that  a persona with a 12 PSTR and a 32.5 kg load would put her into the over encumbered category. Being over encumbered forces her this persona to suffer all Over-encumbered penalties: to movement rate reduced by half, and penalties on performance rolls, ambush and initiative.  This movement penalty is in effect even while wearing or carrying nothing at all. 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. For example the persona’s own body would become too heavy to move if she were in 1.7G, because her own extra body wate would exceed her maximum wate allowance.

Combat: Combat is very likely in a high gravity situation, because where-ever there are personas there is likely to be combat. The effects of additional wate to weapons, shortened trajectories, and varied deflections can greatly hamper a persona’s ability to hit a target. There are five categories of gravity to-hit penalties, and they are based on the encumbrance level of the affected persona. The penalty includes the new wate of the weapon being used, the different speed of attacks, and the complications of body wate discussed earlier. These penalties are given on Table 19.2: Hi Gravity To Hit Penalty.

Table 19.2 High Gravity and Combat

Encumbrance plus high gravity makes maneuvers exponentially more difficult.
EncumbranceTo hit penalty
EncumbranceTo hit penalty
Over Encumbered-300
Lift Only-500 (lift limbs only)

Let us consider our hapless traveler with a wate of 65 kg, and a 12 PsTR. On a 1.5 g planet she would have to attack with the over encumbered gravity penalty of -300 on all to hit rolls. If the additional wate of the weapon were to push her into the lift only category, she may be able to pull the trigger, but not carry the weapon. Only gravity and trajectory dependant weapons are affected. This automatically includes all type A and B weapons and most type C weapons. Weapons excluded from gravity penalties are laser, sonic, ray, radiation, and stun weapons. These weapons are only excluded from the to hit penalties when the the persona is in the free, unencumbered, or encumbered categories. If the persona is more than encumbered due to her body wate, she has been overwhelmed by the gravity and the penalties still apply.

Ranges: Weapon range reductions apply in much the same manner as the to hit penalties. All type B, and most type C weapons are affected by range reductions. The range of the weapon is divided by the increased gravity, and the rate of decay of the weapon is multiplied by the gravity. For example, a crossbow has a range of 25 hexes with a penalty of -125 per hex beyond 25 hexes. On a 2 g world the same weapon would have a range of 13 hexes, and a penalty of -250 per hex beyond 13 hexes plus what ever gravity encumbrance penalties apply. Weapons excluded from range gravity penalties are laser, sonic, ray, radiation, and stun weapons. The area of effect of grenades is reduced by HIG to the same degree as the range of a projectile weapon. A grenade which uses shrapnel has its radius of effect divided by the gravity. For example, a chemical explosive grenade (#2 Grenades/aerosols in the Tech list) exploded on a 1.5 g world would have its radius of effect reduced from 6 hexes to 4 hexes (6/1.5)

Damage: The damage of type A weapons is increased with increased gravity. A type A weapon (thrusting and striking weapons) in a 1.2 g world would inflict 20% more damage. This is primarily due to the increased wate of the weapon. The additional damage inflicted because of gravity cannot exceed double damage. Type B and C weapons are not included in this damage bonus because their damage is derived from the velocity of the projectile.

Since higher gravity causes everything to accelerate more, objects are moving faster when they hit the ground than they would be in normal gravity. This phenomena increases the damage of falling or dropped objects. Damage from falling is increased identically to that of the damage oftype A weapons. Falling objects will also inflict greater damage, by the same percentage as the increased gravity. Neither of these damages can be more than doubled due to gravity effects.

Performance Tables: The effects of high gravity on the performance of class skills is left up to the referee. Tools have a greater wate, creatures move differently, wounded bleed faster, etc. The referee may wish to apply a flat DD penalty, like the encumbrance penalty found on Table 18.3: Encumbrance and Performance Rolls. However those performance rolls for maneuvers that represent mental processes not affected by gravity. 

Long Term Biological Effects: Very high gravities (greater than 2G) cannot be suffered for extended periods of time. Personas can adapt to high gravities if they are exposed to them over long periods of time. A persona’s PSTR, can increase until her new wate (at the higher gravity) can be handled in the encumbered category. If a persona is in the free, unencumbered, or encumbered, categories due to gravity encumbrance, there is no training effect, and no gained PSTR due 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 own body wate. Her PSTR would increase until she was in the encumbered category when supporting her own wate. This improvement will progress at the rate of 1 new point of PsTR for every 12 months of uninterrupted high gravity. This persona could increase her PSTR. from 12 to 16 with a 4 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 that 12 month period.

The PSTR bonus can only be awarded if the persona finds herself in the over-encumbered category. If the person has a gravity encumbrance penalty of ‘lift only’ her system has been overwhelmed, and no PSTR increase can be earned. If personas are using space travel, or other means, to unrealistically increase their PSTRs several penalties may be evoked by the referee: make the higher gravities difficult to obtain, or find; create an unforeseen side effect when returning to lower gravities; or simply put an attribute maximum on the amount of HIG training possible.

The ref can shorten the time needed for PSTR increases with special high gravity training clinics. There are no other attribute bonuses to be obtained by exposure to high gravity. If personas overeat in order to gain wate for an improved HIG training effect, they should suffer the extreme consequences of their bad nutritional habits (atherosclerosis, cancer, allergies, etc.).

Mechanical Effects: The mechanical limits of inorganic objects in high gravities are much less restrictive than biological limits. This is generally the case because alloys and textiles used in equipment are much stronger than biological fleshes. The mechanical limits of equipment where fluids are of primary importance are severely limited by high gravity.

The most important effect of high gravity on a mechanical system is its added wate. This added wate will increase wear and tear, reduce the effectiveness of lubricants, and severely increase fuel consumption. Electrical equipment is unaffected by increased gravity, but some batteries (such as gravitational batteries) are affected, and that may cause a piece of equipment to break down. The total effect of high gravity on equipment is very much left to the imaginative logic of the referee. A check to see if all of the equipment’s components can survive the new gravity is a great opportunity for Sphincter Dice (Chapter Special Rolls).

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 actually zero gravity (ZOG) is whether a persona is in danger of achieving escape velocity through her own movements. An expedition may find low gravity (LOG) surroundings on small planets, or asteroids. There are even some devices which develop anomalous low gravities. Low gravity is generally beneficial to the persona because it reduces the strains of Wate allowance, which allows for easier movement with larger amounts of equipment.

Wate: 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 normal. A persona with a wate of 80 kg would have a wate of 40 kg in 0.5G. This means that the persona is carrying 40 kg less than she normally carries. 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 vehicle with a wate of 2000 kg would immediately have the capacity for another 1000 kg of cargo on a 0.5G planet.

Movement: Low gravity doesn’t immediately yield faster movement rates for the personas, but it does allow them to move the same speed they normally do with greater amounts of equipment. The wate that an 80 kg persona would lose in 0.5G is added to her wate allowance. If the persona had a 12 PSTR her 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. Occasionally this will have a  drastic effect on the psyches of equipment crazy players and the ref may have to consider the sheer volume of the items that they’ll try to carry.

The persona who’s wate is 80 kg and PSTR is 12 would move no faster on a 0.5G world than she could on a 1G world. The difference is in the encumbrance effect on movement. This persona could act unencumbered while carrying 14.25 kg of equipment. Personas can sprint in low gravity as if it were normal movement. If the persona’s equipment wate is greater than her new wate allowance can bear, normal encumbrance penalties will apply.

Combat: When the personas become light bodied in low gravity, they may also become light headed, which may lead to combat. The changes in trajectories, wate of weapons, and body balance all have an effect on LOG combat. Any changes to the parameters of one’s combat skills is not good. Type B attacks may fly further, but they don’t follow the same trajectory. Type A weapons are easier to wield, but they don’t have the same crushing wate as before.

To hit adjustments When such differences are taken into account, there is an overall detriment to the to hit roll in low gravity combat. The effect isn’t as dramatic as that of high gravity, but there are penalties all the same. The bonus proficient (BP) of the persona is reduced in proportion to the low gravity. For example, in 0.5G the persona could use half her bonus proficient (BP), and on a 0.25G planet she could only use 1/4 her bonus proficient (BP) because the gravity is even less familiar. If our persona had a BP of 142 she could only add 71 to her to hit roll when in 0.5G. Type A and type B weapons are affected by this bonus proficient penalty, type C weapons are not. Grenade accuracy is affected by this penalty as well. 

Range The distance of attacks, as far as their maximum range is concerned, does increase, but their 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 same ranges are used to determine the accuracy of the attack, but the projectile may travel much farther than normal.

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. In 0.5G the weapon would have a range of 50 hexes, and a rate of decay of -63 to hit per hex after that. This means that the bolt will travel 66 hexes, but useful accuracy would not change. Not all weapons are affected by low gravity range increases, for instance, laser, sonic, ray, radiation, and stun weapons have no projectile to be affected by gravity.

Shrapnel area of effect weapons are unaffected by low gravity. The shrapnel of the attack will definitely travel further, but the density of the shrapnel will be reduced at this greater distance, so the damaging area of effect is no different. For example, if the radius of effect of a grenade is 6 hexes, and it were used on a .5 g world the shrapnel would travel twice as far, but the damage area would still be 6 hexes.

Damage: The damage of an attack is unaffected by gravity. TyPe B, and type C, weapons are unaffected by gravity because their damages are dependant on horizontal velocity, and not downward gravity forces. Type A weapons are unimpaired as well. The gravity aided momentum of the weapon may be reduced, but the force of the attack should be sufficient to overcome this.

Since everything accelerates less in a low gravity, objects will be moving slower when they hit the ground. This causes the damage of falling, or dropped objects to be less. The effects of low gravity on combat seem to be detrimental, but there are some advantages for the personas if they should happen to fall, or have things dropped on them. Damage for falls, and falling objects is generated normally, but it is then multiplied by the gravity present (less than 1 in low gravity). So a fall on a 0.5G planet would inflict 1/2 damage, and falling objects on a 0.25G asteroid would inflict 1/4 damage.

Performance Rolls: Low gravity has no effect on the performance rolls. Rolls on the performance table may be subject to a short term DD penalty while the personas adjust to the unfamiliarity of the new gravity. In the long run, due to reduced encumbrance, the personas may find that low gravity has a beneficial effect on their performance tables.

Biological Effects: Low gravity has no short term detrimental biological effects. Personas are unaffected by decreasing gravities, and even zero gravity does not harm a persona, unlike high gravities, where increases can crush a persona. The only short term effect of low gravity may be nausea caused by loss of equilibrium in the inner ear. The disabling effect is more common as the gravity becomes less and less. Each member of an expedition must be checked to see if low gravity sickness affects them.

Low Gravity Sickness: There is a percentage chance equal to the gravity in a location that the persona will NOT be afflicted by low gravity sickness. Thus there is a 50% chance of being disoriented at 0.5G, and a 75% chance of being disoriented in 0.25G. If the persona is having a bout of LOG sickness she must save versus intensity d20 psionic attack, or become incapacitated with nausea (Chapter 16 Special Rolls). If she resists the attack there will be no disorientation will be no effect Personas afflicted by LOG sickness are suffering from disorientation of the vestibular canals found in the inner ear. This causes light headedness, dizziness, and nausea, as the system tries to maintain balance for a 1G world. The effects of the sickness will afflict the persona for 2 to 24 (2d12) hours, after which the persona will spontaneously recover.

Long Term Effects: The long term effects of low gravity can be quite hazardous to the persona. The lessened gravity will atrophy muscles, reducing PSTR, and dilute blood reducing CON. The personas should not be terrified of low gravity attribute effects, because they happen over a long period of time and personas quickly recover once back into 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 ad 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 red blood cells in the bone marrow, 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 point of CON that month. No more than three points of CON can be lost to low gravity. However, even this loss could kill personas that have very low constitutions, by reducing an attribute to below one. The lost CON can be regained at a rate of 1 point for every 24 hours at full gravity.

Mechanical Effects: Low gravity definitely has beneficial effects on most mechanical devices. There is less internal friction, and power systems have to contend with a reduced work load. The only point that will be discussed here is that of decreased load. A vehicle with a wate of 200 kg at 1G would only have a wate of 150 kg on a 0.75G world. The 50 kg that the vehicle is not carrying means that it can function normally with an additional 50 kg of cargo. Because of the reduced wate, wear and tear should decrease, fuel consumption should decrease, and overall performance should be improved. What is not detailed is the effect of reduced friction required by surface vehicles for movement (cars slide more often), or the effect that reduced gravity has on instrumentation designed for normal gravity.

No Gravity

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).

Otherwise, ZOG is fun for the expedition, but a terror for the referee, primarily because it lends to 3 dimensional movement caused by many unintentional forces. ZOG is not just an extension of low gravity rules, it must contend with many absolutes for which the lo gravity system does not account. Things like ranges, normal movement (ha!), swimming, floating, weapon kickback, and hit knock back, are just some of the problems that arise due to a complete lack of gravity.

Wate: When gravity is absent, wate is absent also. In a ZOG environment a persona can lift virtually anything, and 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 ultimate question about pushing or lifting something in zero gravity is whether the object, or the persona, moves.

Movement: It’s not that ZOG has an effect on movement, but that in zero gravity everything effects 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 the step send the persona flying straight up into the sky.

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 her regular movement rate. When moving in this fashion the persona cannot attack or do anything other than movement, and must gain a foothold before attacking.

Pushing Off Movement: Another method of movement in zero gravity is to push off of a unmoving base, and to fly along with the momentum generated by the push. The problem is that the persona will continue moving until she hits another solid surface, or friction from the atmosphere slows her down. This continuing motion is based on 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 of into oblivion. Zero gravity movement is easily generated, but it can be deadly for the unskilled.

The push method of movement works fine against massive objects, but as the object becomes closer to the wate of the persona; the push becomes less efficient. If the object is lighter than the persona (lower wate) then the object will move away from the persona faster than she will move in her desired direction. A simple process for this is to divide the similar wates together and both take off in opposite directions at the percentage of possible movement rate. So if a 100kg persona tries to push off on a 50kg object (possibly another persona) she will move at 50% of her expected movement rate and the object will move away at 50% as well. Coordinating push offs to optimize movement in ZOG can only be carried out by personas with skill in ZOG.

Even this oversimplified method of zero-g movement may seem unmanageable, but like all EXP systems the referee is not forced to use it. If survival of a persona is at stake, a completely objective movement system may be required, and the push off method should be perfectly adequate.

Combat: In zero gravity  combat forces generate unintended movement. So punching a target and scoring a hit will cause the target to move away if the physics are right. Not all attacks generate movement forces. Weapons like lasers, sonic, radiation, ray, and stun weapons do not generate momentum. Any damage that is generated by delivering force will generate movementAttacks will generate two types of motion: translational motion and rotational motion. Translational motion is very easy to play, the target simply moves in a direction away from the attack. Rotational motion arises from a force which upsets the rotational equilibrium of the target, and sets it spinning.

Translational motion in h/u = 1 h/u per 10 HPS of damage

Low Gravity Sickness Chance = 1 % per h/u of translational motion

Translational movement is easy to convert into play: the target will move at 1 h/u for every 10 HPS of damage inflicted.. The type of weapon inflicting the damage will make a difference as to the resultant velocity. Rotational movement can be end over end, side to side, or a combination of both directions of spin. Such spin may cause the spinning persona to suffer an attack of low gravity sickness similar to that discussed under low gravity biological effects. In reality translational motion would be combined with rotational motion, but the complexities of such resultant forces are well beyond the scope of this fun simulation. Translational motion in zero gravity is cumulative, and if a persona is flying away at 8 h/u, and then gets shot in the back (how callous) for 40 HPS of damage she will continue to move away at 12 h/u. She will then have a 12% chance of getting sick from the rotational motion. This will incapacitate the persona for the remainder of the combat session. The persona will get a saving throw versus psionic attack to not become ill from rotational motion. If the persona is overcome it will only be  for 1d10 units NOT the longer version from low gravity. 

Table 19.3 Zero Gravity Combat Penalties

Maneuvers involving the transmission of force are more complicated in zero gravity (ZOG).
Weapon TypePenalty
Weapon TypePenalty
Type A (hitting)-200
Type B (projectile)-100
Type C (powered)-150
Type D, E, F (multi shot)-150, first -300 second, -450 third

Non-powered Weapons: Type A weapons (thrusting and striking) are very difficult to use in zero gravity. When generating the forces required to do damage results in crazy spinning forces in zero gravity. The persona literally throws herself off balance. In zero gravity this could result in rotational forces after every attack. Instead, purely for convenience and not realism, only translational motion will result for the attacker and target when a hit is scored. Whether they are slowed down, or sped up, by an attack will depend on the direction of the blow. For example, a motionless persona hits a motionless target for 21 HPS of damage. They both will move away from each other at 2 h/u.

This system of resultant translational motion is accurate for personal combat amongst anthropomorphs of equal size. If a light wate persona is hitting a heavy Wate  the above formulas for push-off velocity can be applied to the expected recoil. For example, if the previous attacker scored a hit against a target twice her wate, she would move away at 1.3 h/u and the target would move away at 0.7 h/u.

Type B weapons (non-powered projectile weapons) will not generate any translational or rotational motions for the attacker. However if a hit is scored the target will suffer 1 h/u of translational movement for every 10 HPS of damage rolled.

Powered Weapons: Type C weapons are powered projectile weapons. Most guns generate significant translations motion for the firer.  Most type C weapons generate translational forces for the attacker every time the trigger is pulled. All guns will produce kickback in zero gravity unless specifically stated 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 1 h/u per 10 HPS of maximum damage possible. In normal gravity, if the weapon is being held properly, the persona will absorb the kickback force and not move. In zero gravity all of this force generated by the exploding bullet is converted into translational energy for the firer. In zero gravity the target will only gather translational motion if it is hit. A hit target will move in the opposite direction of the attacker at a speed of 1 h/u per 10 HPS of damage. Grenades which generate projectiles or forces will also generate movement of targets within the area of effect. The targets will move away from the target hex (epicentre) at a rate of 1 h/u per 10 HPS of damage.

For example, a XHP revolver inflicts 4 to 48 points of damage. When fired the attacker will move at 5 h/u  (max damage is 48 HPS) away from the target. Assuming the target was hit for 12 HPS of damage, the wounded target would move in the opposite direction at 1 h/u.  

Training:Unless the persona is trained in zero gravity combat, or is using a weapon specifically designed for zero gravity, she will suffer the following penalties as per Table 19.3: Zero Gravity Combat Penalties. If the persona is trained in zero gravity combat all her bonuses will apply as normal. 

Range: There is no change to the accuracy of ranged weapons, but the projectiles will carry on indefinitely. For example, a crossbow fired in zero gravity would still be completely inaccurate beyond 33 hexes, but the projectile will continue travelling until stopped by atmospheric friction or a solid body.

Damage: Damage is unchanged for any weapon attacks in zero gravity. The reasoning behind such conclusions is detailed under low gravity combat effects in this chapter.

Performance Rolls: The effect of zero gravity on performance roll are identical to those of low gravity discussed earlier in this chapter. Zero gravity essentially has no effect on the performance of maneuvers, and irritating effects like tools floating away will be more serious than the total effect of zero gravity.

Biological Effects: Watelessness can be just as problematic as low gravity on biological systems. All of the detrimental short and long term biological effects will occur zero gravity. They are all administered the same way, so loss of PSTR and CON are guaranteed in zero gravity. Zero gravity sickness is the same as low gravity sickness, and is administered in the same fashion.

Mechanical EffectsZOG can have drastic effects on mechanical equipment. Any device which depends on friction, levers, or counterbalances may not function in zero gravity. This does not mean that nothing will happen , but that nothing normal to the 1G world will happen. A vehicle’s combustion engine would spin the wheels, but if the vehicle is floating 10 cm off of the ground the car 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. If a dispute arises refer to the Sphincter dice, as described in Chapter 16: Special Rolls.

Equipment that is designed for zero gravity such as vac-suits, or spacer equipment, need not be subjected to this check. Many mechanical devices which have proven their worth in zero gravity need not be tested either: knives, golf clubs, pistols, pens, etc. What the roll is designed for is the black box technology that neither players, referees, or authors understand the workings of. Some examples are psionic detectors, robots, age determiners, force field generators, etc.

Stylish and alive.
Stylish and alive.

Atmospheric Effects

Atmospheric effects are only concerned with the condition of the atmosphere inhaled by a persona. The atmosphere may be generated by the life support system of a ship, the recycling unit of a vac-suit, or the environment of a planet. Regardless of how the atmosphere is generated, normal atmosphere is called 1 ATM.

Similar to the generic 1 G, 1 ATM will have the ideal conditions of atmosphere for an anthro persona to survive in. 1 ATM has both the correct air composition, and the correct pressure for breathing. Any changes from 1 ATM will have detrimental effects for the persona. Lungs have a very restricted range where they can they can transfer oxygen into the blood (or carbon dioxide into the sap) and any changes to the atmosphere, whether in composition or pressure, will have drastic effects on anthro and alien types.

Changes in atmosphere (ATM) usually result from exposure to very high altitudes, or exposure to the vacuum of space. High ATMs usually occur on the surface of massive planets, which usually means that the effect is combined with high gravity. The general principals of low ATM are easy to grasp: remove the atmosphere and the personas die. Exposure to space will remove all atmosphere, and kill the personas. Exposure to exatmo will usually be accompanied with zero gravity.

A change in atmosphere accompanied by drastic biological and mechanical side effects. The effects of a vacuum on wate, movement, combat, and performance tables are insignificant when compared to the biological effects. These game procedures are more affected by gravity than by atmosphere. Atmospheric, and gravity effects are cumulative. Atmosphere has no direct effect on the wates of equipment or the wates of personas. If a persona’s wate has been reduced significantly due to low atmosphere she is certain to be dead. High ATM makes the persona carry a heavier atmospheric load, and literally crushes the persona.

Movement: Movement effects due to atmospheric changes are not significant. If a player expects her persona to move faster because of reduced air friction, she would have to contend with both a vac-suit, and zero gravity, which would certainly counteract any movement bonuses due to reduced friction.

Combat: Physical properties are unaffected by the quality of the atmosphere. To hit rolls are unaffected, damages are identical, and ranges are the same regardless of the atmosphere in which combat takes place. Many type C weapons will not work in a vacuum because they are dependant on atmosphere to function. How atmosphere affects mechanical devices is discussed later.

Performance Rolls; Performance table rolls are unaffected unless the persona is protected by a bulky space suit. If the persona is protected then the restrictiveness of the protection will hamper performance rolls. If the persona is unprotected from a vacuum, then survival is of primary importance, and performance rolls will not be significant.

High Atmospheric Pressure

High atmospheric pressure will cause increased wate on the persona because more gas in the atmosphere than normal is resting on the persona’s head. In normal planetary atmosphere a persona is supporting a column of air on her head. In 1.5 ATM 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 lungs. If the atmospheric pressure continued to increase, the persona’s eyes would push in, her lungs would collapse, and eventually air would force its way into the body through mucous membranes.The effect of high atmosphere on personas is left for the referee to determine for her milieu. Whatever biological parameters are employed by the referee they should apply to all humanoid races equally. Essentially a high atmospheric pressure quickly crushes the persona, alien or robot to death.

Low Atmospheric Pressure

The effects of low atmosphere are listed as fractions of  1 ATM. They represent progressively worse conditions of exposure to low ATM, the categories are hypoxia, dysbaria, anoxia, and ebullia. Each is detailed below.

Normal (1 ATM to 0.70 ATM): Normal atmosphere has no detrimental effects on any of the anthropomorph races (except aquarians). The parameters of this normal range are only included for comparison.

Hypoxia (0.7 ATM to 0.41 ATM):  The respiratory system is having trouble exchanging the persona’s essential gages. Lungs are having difficulty getting oxygen into the blood, which ultimately results in a shortage of oxygen to the tissues. Or maybe the sap does not have enough CO2 to deliver to the skin for photosynthesis. When the tissues have an essential gas debt, light headedness will result. A normal CON attribute rolls (d20) will be required to resist fainting spells when vigorous activity is undertaken. The fainting spells can be induced by activities such as standing up too fast, running, or getting into combat. A failed normal CON attribute roll will result in a swoon and blackout that lasts  1 to 20 units (1d20).

Dysbaria (0.40 ATM to 0.12 ATM):  Dysbaria is the formation of undesired gas bubbles (primarily nitrogen) in the blood and tissues of the persona. When pressure surrounding the body drops, nitrogen can be released in gaseous bubbles which attack the nervous system. This effect can vary from extreme discomfort to death. When subject to an attack of dysbaria the persona must save versus an intensity 4 to 16 toxin (4d4). A dysbaria attack will inflict 1d4 per point of intensity. The damage is halved if the persona makes her save versus toxin. A persona exposed to 0.3 ATM pressure would suffer an immediate dysbaria attack. The attack has an intensity of 10. The 10d4 roll indicates 27 hit points of damage. If the persona makes her save versus intensity 10 toxin she will take only 14 HPS  of damage. Personas suffering from dysbaria, also suffer from Hypoxia and must make a hard CON attribute roll (1d30) or pass out  out for 1 to 20 units.

Anoxia (0.12 ATM to 0.06 ATM): Anoxia is the lethal advance of hypoxia. This occurs when the essential gases (CO2 or O2) are so thin in the atmosphere that life cannot be sustained. Any organic persona exposed to this low an atmospheric pressure is simply suffocating.

A suffocating persona stay conscious for a number of units equal to her CON. After which she will go unconscious and will be irretrievably dead and within 1 minute per 4 points of CON (a minute equals 30 units). There is no saving throw awarded. While the persona is struggling to remain conscious she will be subject to a dysbaria attack of intensity 6 to 24 (6d4), and must save versus toxin or take the prescribed damage. There will also be one hypoxic attack during the pre-unconscious period of Anoxia, this may render the persona unconscious immediately.  Personas rescued before dying are subject to a second dysbaria attack like the one above when being resuscitated. Personas exposed to an anoxic level decompression stand a very high chance of dying, regardless of rescue.

A persona with a 12 CON is exposed to .1 ATM after a starship’s hull has been ruptured by a missile. She could remain conscious for 12 units. She will be subject to one attack of dysbaria and one attack of hypoxia. If she managed to remain conscious for the entire 12 units and was unable to reach safety she would become unconscious. If the unconscious persona is not rescued within 3 minutes (90 units) she would be dead. It is that simple. If she is rescued she will have to survive another attack of dysbaria before being successfully resuscitated.

Ebullia (0.05 ATM to 0 ATM)Ebullia results from the body being exposed to a vacuum. Ebullia indicates that all the bodily fluids are roiling into a gaseous form as there is no pressure to keep them liquid. The body fluids immediately vaporize, and escape through the mucus membranes of the body (eyes, mouth, etc.). The body is essentially boiling. Ebullia from being exposed to a vacuum is almost certain death.

A persona can remain conscious for 1 unit per 4 points of CON. Once unconscious the persona can survive for 1 unit per point of CON. After this time frame the persona is dead.  There is no save, and death from ebullia is final. While struggling to remain conscious the persona must survive a dysbaria attack of intensity 8-32 (8d4). They are also likely to become immediately unconscious due to hypoxia. The persona must beat tough CON attribute roll (1d50) to keep from fainting. If the persona is saved before dying then they must survive a second dysbaria attack when being resuscitated. Being exposed to a vacuum sucks. 

Mechanical Effects: Artifacts and Low Atmosphere. Low or zero atmosphere should not be confused with low or zero gravity. Mechanical functions such as levers and pulleys will function normally regardless of atmosphere. Those mechanisms which are adversely affected are those which depend on chemical reactions to function. Self contained chemical reactions (like bullets) will function even in zero atmosphere. Machines whose mechanisms are not understood, those little black boxes, like age determiners, ammo detectors, or psionic helmets, are subject to the imaginative logic of the referee. A check to see if all of the equipment’s components can survive the new gravity is a great opportunity for Sphincter Dice (Chapter Special Rolls). Obviously equipment designed to function in vacuums like safe suits, and exatmo equipment should not be subjected to malfunction. 


This part of special terrain is devoted to underwater adventuring. The rules can be applied to virtually any sub-liquid atmospheres which the personas may find themselves in. Water is essential to life for all anthropomorph species; however, an entirely water environment is also lethal (except to aquarians). If a persona finds herself immersed in liquid without proper breathing apparatus she will be killed by anoxia (absence of oxygen). She will drown. Once the survival complications of water adventures have been overcome, the persona will suffer massive movement restrictions, combat penalties, and other kinds of impairment. The deeper below a liquid’s surface, the greater the pressure the expedition is subject to. Water pressure can easily crush equipment as well as personas. The damaging effects of water pressure are covered under biological and mechanical effects

Wate : The buoyancy (tendency to float) of an object will help reduce its wate when submerged in water. For personal equipment, an object’s wate will not be reduced because there is sufficient drag to account for the encumbrance effects. The equipment may have a decreased wate, but it still must be pulled through the water. Moving one’s hand first through the air, and then through water should demonstrate this effect. Adventuring in liquids other than water will affect the buoyancy of objects drastically. The density of the liquid determines buoyancy, so liquids less dense than water will support fewer substances (wood or plastic may sink), and liquids more dense than water will float more substances (lead floats in mercury). For adventures in liquids other than water, it is up to the referee to do her research. .

Movement: To say the least, underwater movement is completely foreign. Not only must the body deal with the restrictiveness of a protection system, it must deal with the 1000 times greater drag of the dense water. Water is very dense compared to air. Usually personas will sink to the bottom of whatever body of water they are exploring, 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.

Walking: A persona walking through water may move at 1 h/u per 6 points of PSTR. Thus a persona with a 14 PSTR could push along at 2 h/u. The effects of WA on movement cannot reduce the persona’s movement below 1 h/u. If the persona’s uncumbrance is in the lift only category she may not move. The persona can also sink at a rate of 1 to 4 h/u depending on the buoyancy of the equipment carried. A persona can safely sink off he edge of crevasses, and float down at 1-4 h/u (1d4). Falling is not a concern.

Swimming: Swimming will allow the persona to move at 1/5 her on land movement rate. A persona may only do this if she is skilled at swimming. Aquarians can swim at the movement rate designated by their DEX. Once swimming is affected by encumbrance it will rarely be faster than walking along the bottom; however, swimming allows for 3 dimensional movement around obstacles and above targets.

Combat: The results of underwater combat are as futile as attempts at underwater movement. Because the effects are so drastic, and varied, the parameters of each weapon type is listed in the following paragraphs.

Type A WeaponsType A weapons are non-powered thrusting and striking weapons. Only thrusting attacks may be used underwater, and weapons with a primarily striking attack are useless. A mace, flail, axe, bo-stick, and hammer are examples of striking weapons that do not work underwater. Whereas a trident, spear, or point are examples of thrusting weapons that would work under water. Type A thrusting weapons have a to hit penalty of -200, while striking weapons cannot be used at all. The damage of successful thrusting attacks are unaffected by submarine situations.

Type B Weapons:  Type B weapons are non-powered missile weapons such as axes, spears, bows, and objects. Such weapons cannot be used underwater at all. The density of water offers too great a drag for the weapon to be of any use. Type B weapons can be used as their type A alternates to inflict thrusting damage.

Type C WeaponsType C weapons are powered weapons such as guns, pistols, and rifles. Because of the effects of water on sighting, ranges and other detriments, the attacker will receive a -342 to hit roll penalty. Type C weapons do not have their damages reduced, but their range is drastically shortened. The range of useable type C weapons underwater is 1/10 of normal range. So a crossbow with a range of 25 hexes, and -125 to hit per hex beyond 25 hexes would be reduced to a range of 3 hexes and a penalty of -1250 for every hex beyond 3 hexes. Effectively creating a 3 hex maximum range.

Grenades: The most drastic effect of using grenades underwater is that cannot be thrown underwater cannot be thrown any significant distance from the expedition— remember no type B attacks. Water has a very stabilizing effect, and grenades are designed to create chaos. Once a grenade is detonated underwater, its area of effect becomes a subject a great debate. Grenades like sky lighters, gas grenades,  phosphorous fires, and smoke clouds will not function under water. However the area of effect of a concussion grenade may be increased.   Aerosols simply do not work underwater.P

Performance Rolls: Water has a dampening effect (pun intended) on the senses of the persona. Touch is hampered, sight is affected, and smell and taste are useless. This, of course, is not true for aquarians. The persona must also deal with equipment that wants to float away, sink, or dissolve. The complications are endless, and personas receive a +7DD penalty when attempting maneuvers underwater.

Drowning: The immediate biological effect of water immersion at any depth is anoxia. Anoxia is the absence of the oxygen needed for the lungs to transport into the blood (or the absence of carbon dioxide for the sap), and death quickly results. Underwater anoxia is also known as drowning. A drowning persona will be unconscious within 2 units per point of CON, and dead within 1 minute (30 units) per 4 points of CON after falling unconscious. 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.

Attributes: If the persona has devised some form of defense from the water, she may survive without worry of anoxia, but she will suffer a penalty of -3 on all attributes while in the liquid environment. This is the reverse of the aquarian’s out of water penalty. Aquarians function with their rolled attributes while in water. Aliens that have some liquid movement are also unaffected by being underwater.

Water Pressure: Including the already described biological deterrents, the persona must also deal with water pressure as she descends deeper and deeper into the water. The effect is very simple, as she descends she puts more and more water above her, and this water pushes down with more and more force until it crushes her to death. For example, the wate of water at a 5 hexes deep is about 420 kg, at 50 hexes it is 4200 kg, and at 5000 hexes it would be around 42 tonnes. A persona could not venture below 25 hexes underwater without pressure protected gear. If personas still insist on going deeper, or if something else is insisting, they will take one d4 damage per unit for every 5 hexes they are below the 25 hex limit. The pressures of deep water will certainly crush to death personas and whole expeditions.

Depressurization: If a persona is subject to the increased pressures, she may rush back up to safer depths to avoid being crushed. When an organic creature suddenly goes from high pressure to lower pressure it is similar to being exposed to low atmospheres. Rapidly depressurizing personas will suffer a dysbaria attack (see low pressure above). If the persona rises to the surface faster than 3 h/u she will suffer a dysbaria attack. Dysbaria is the formation of gaseous bubbles in the blood and tissues. When a dysbaria attack is indicated the persona must save versus intensity 4 to 16 toxin.

Mechanical Effects: Electronic equipment immersed in water is cannot function and is usually destroyed. Electronics will suffer electrical impulses jumping randomly across connections, charging and depleting components with reckless abandon. Water immersion is the ultimate short circuit. Toys and equipment with electronic components, and those which depend on a gaseous atmosphere cannot function underwater.  If an artifact is damaged by immersion or not depends on the imaginative rationalization of the referee. If a dispute arises refer to the Sphincter dice, as described in Chapter 16: Special Rolls. Equipment that is hardened for EXATMO or low pressure or underwater will not be destroyed and may even function. 


As odd as it may seem in the context of such obvious terrain features as vacuum, or high gravity, fire is an environmental condition likely to be encountered by an expedition (particularly in the midst of combat). As experienced with carnage and conflagration as most personas are many do not understand the implications of  detonating fuel air explosives in the tinder forest in which they are standing. The below rules are for incidental fire exposures, not successful fire attacks. A successful fire attack (like a napalm gun) will have specific rules of damage and burning. Fire in this Special Terrain chapter is incidental exposure by being trapped or nearby an open flame.

Common Combustion: A flame that is consuming dry, fibrous material such as wood, paper, organic cloths and/or rope will  inflict 3 – 30 HPS (3d10) of thermal damage every unit the persona is in the flaming hex. This does not mean that a persona walking beside a campfire will take 3d10 HPS damage. However a persona runs through a wall of flame would take damage for each unit in the fire. Once the persona is “playing with fire” there is a chance they may immolate. The percentage chance of clothing catching on fire is equal to the damage rolled. Clothing will burn until gone or until the flames are smothered. Burning clothing will inflict an additional 2 to 20 HPS of damage (2d10) for every unit it continues to burn.

Accelerated Combustion: If the fire is being fed by some form of fossil fuel, petroleum-based plastics, glowing radiation blob,  phosphorus or magnesium it will inflict more damage per unit. An accelerated fire will do 6-60 HPS of thermal damage (6d10) to any persona in the burning hex. Even if the persona is buck naked (a less than desirable condition in event of a chemical fire), they have a percentage chance of immolation equal to the damage rolled. If they catch on fire, the persona will suffer 2 to 20 HPS (2d10) of additional damage per unit for 1 to 10 units (1d10).

Smoke: Fire burns, smoke kills. Even if the persona avoids the fire the smoke may still get her. Smoke will spread even where fire cannot get to. 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 local air supply.