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As is true with most RPG's, GAMMA WORLD has as many rule variations as it does Game Masters. I am no different. So, here is my version of the game: (feel free to use anything you find here. I don't get to play much, so somebody should use it!)
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Character Types
Die Casting
Character Generation
Improving Your Character
Poison and Radiation

This version has revised die-casting rules to make it more realistic. It also has new Mutation lists. Some of the old Mutations have been kept and/or modified, while others have been tossed. These rules are to be used in conjunction with the original game system, not instead of them.

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You can be just about anything in GAMMA WORLD. You can be a Pure Strain Human - PSH (called Pure Ones in this version), or a Mutant. Mutants can be mutated Humans or Animals. Any mutated animal is automatically given two "free" Mutations not listed with the Mutations below: intelligence and the ability to speak. Now, this does not mean that the Player of a mutated animal is bestowed with smarts, just his Character.

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Your Character will need Statistics (Stats) if he is going to do anything. Here is a description of what they are and how they work in this incarnation of GAMMA WORLD.

STR - Formerly PS, this is the Character's Physical Strength. The scores are size based. A character that is the weight of an average human male (175 - 300 pounds) can have a maximum of 17. Those larger have a maximum of 20, those smaller have a maximum of 15. These maximums can only be raised by mutations. Strength has as much to do with how well you do something as it does how strong you are.
WILL - Formerly MS, this is the Character's strength of mind. It is the same for all Character races. This increases at 1 point for every 2 points of INT gained.
INT - Two languages are allowed for an Intelligence up to and including 16, three for INT 17-19, four for INT 20. This Stat is the same for all Character races and can only be increased by schooling.
DEX - Covers both manual Dexterity (hands, feet, fingers, and toes) and bodily agility. This Stat is raised by physical training or mutation and is the same for all Characters.
CON - Constitution determines, among other things, how many Hit Points (HP) the Character has. Constitution scores are limited by Character types: Pure Strain Humans have a maximum of 20, Mutants have a maximum of 17. This Stat can be increased only by training for PSH characters. Mutants can also increase this by mutation.
HP - Hit Points are the amount of damage that a Character can take and still survive. Unlike the previous six Stats, HP are randomly rolled, not chosen, and are related to size (see CHARACTER GENERATION ).
All Stats, with the exception of HP have a maximum of 22.

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When you need to perform an action, you must determine what number needs to be rolled. To do so, pick the Stat or Stats appropriate to the action and determine the average amount over 10 for each of those Stats. Every action has a base chance of 7 out of 20. Add the average from above to 7. That result or below on a d20 is what is needed to successfully complete the action. A "natural" 1 ALWAYS succeeds, a "natural" 20 ALWAYS fails.
If a Stat is below 10, the amount below 10 is added to the die roll (which is bad, see COMBAT below).
Example: STR and DEX are needed to determine if Garrr, the Lizard Man can hit a tree with his sword (Garrr isn't too terribly smart sometimes). His STR and DEX are 19 and 13 respectively, so...STR is 9 over 10, and DEX is 3 over 10. That averages to 6 {(9+3)/2=6}. Add that to 7 and...ta-da! Garrr must roll 13 or under on a d20 (not counting any modifiers, (see MODIFIERS below) to hit that menacing tree.

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Step 1: Decide what kind of Character you want, a Mutant or a Pure One. Mutants go to Step 2, PSH's skip to Step 4 .

Step 2: To Start, you are allotted 8 points to "buy" Mutations. You can have any combination of Mutations that you can buy. The Mutations all have a point value of either 1, 2, or 3. These are the cost to "purchase" the power. Any Mutations that have a prerequisite will require the purchase of both Mutations. Choose wisely! These will be the Mutations that your Character has for life!

Step 3: Write the Mutations on your character sheet. Some Mutations will modify Stats, so keep in mind the modifications. You will be taking them into account next.

Step 4 : Adjust your Stats; Each Stat (STR, WILL, INT, DEX, CON) has a base of 10. Mutants, you get 15 points to "spend" raising these Stats anyway you desire. PSH's, you get 25 points.
If you want more flexibility, you can take a Stat below 10, using the taken points to raise another Stat up to its maximum. There are penalties for Stats below 10, though (see DIE CASTING and COMBAT ).

Step 5: Mutants, pick your race. You can be Animal (any kind), or Human. If you pick a race that compliments your Mutations, it will make things more interesting.

Step 6: With your Game Master's help, determine your base Movement rate for your species (see MISCELLANEOUS RULES-Movement below).

Step 7: Choose your age, height, weight, hair and eye color, and handedness.

Step 8: Determine your Hit Points by rolling d6xCON. Re-roll ALL 1's that come up and add the total from all dice. Body size will modify this total. If you are more than 50% larger than an average human, add 1/3 of your Hit Points to the total. If you are less than 25% the size of an average human, subtract 1/3. The final result is your Hit Point score.

Step 9: Pick an occupation. It can be anything at all. Try to make it go along with your Stats and/or Mutations.

Step 10: Pick two Personality Quirks (paranoid, loner, etc.). They can be anything at all, just as long as they are playable.

Step 11: Determine your Hit and Defense Values:
Hit Values: Base 7.
To Hit w/ Hand Weapons - Average of amount over 10 on STR and DEX, add to 7. This or below on d20.
To Hit w/ Aimed Weapons - Average of amount over 10 on INT and DEX, add to 7. This or below on d20.
Mental Attacks - Amount over 10 on WILL, add to 7. This or below on d20.
Defense Values: Base 7.
To Defend w/ Hand Weapons - Average amount over 10 on INT and DEX, add to 7. This or below on d20. A successful roll halves the damage. Notice that this is the same as Aimed above.
To Dodge - Amount over 10 on DEX, add to 7. This or below on d20. A successful Dodge negates the damage.
Mental Defense - Amount over 10 on WILL, add to 7. This or below on d20. A success negates effects or damage.
Of course, ALWAYS round out the fractions.
Don't forget, if you have a 10 and 14, for example, the average would be 2 {(4 + 0)/2}, NOT 4.

Step 12: Write down your Class Skills. See your GM for what he thinks these should be. Determine the value needed to successfully perform the skill using the same formula used for combat values. All Class Skills begin at Level 0 (that is, no penalty). See SKILLS .

Step 13: Pick your "Other Skills". PSH's get 5, Mutants get 2. Determine the value needed to successfully perform the Skill. All "Other Skills" begin at Level 0. Your GM should provide a list of skills.

Step 14: Give yourself 50 Status points and 200 domars. The domars are your money. Status points will be covered later.

Step 15: Get your GM to tell you how to go about equipping yourself (after all, no two GM's have the same policy on this).

Step 16: Pick the weapon with which you will have Familiarity . See WEAPONS and MODIFIERS for more details.

Let's take Garrr, the Lizard Man for our example again:
Clay decides to play a Mutant in the upcoming game. He chooses QUAKE GENERATION (2 points), INVISIBILITY (3 points), and FORCE FIELD GENERATION (3 points).
Clay then spends his 18 Stat points this way: STR 19, WILL 10, INT 10, DEX 13, CON 13.
Liking what has turned up, Clay decides to make Garrr a Lizard Man, or, if you prefer, a Mutated Kamodo Dragon. Garrr turns out to be 9 feet tall, weighing 1000 lbs., and has no hair. He is 25 years old, has green eyes, and is left handed. His base speed is 4.
Next, Clay rolls 13 (CON) 6-sided dice coming up with 70 Hit Points. Looking above, he is 9 feet tall and 1000 lbs., so you can say confidently that he is more than 50% larger than an average human. Therefore, he would add 23 to his HP (70 X .33 = 23.1, rounded to 23), bringing the total to 93.
He has no occupation except adventurer (read: wandering bum). He likes to point his pistol-grip MK-VII blaster (with which he is Familiar ) at people and smile a large, fangy, lizard grin. His personality quirks are a pathological hatred of birds or birdlike creatures (he will go to any extreme to kill them) and greed.
Using his Stats, his Hit Values are: Hand 13, Aimed 10, Mental 7. His Defense Values are: Hand 10, Dodge 10, Mental 7.
His Skills and Values are; Survival (7), Perceive (7), Deduction (7), Know Item (7), Know Dialect (7), Animal Handling (7), and Know Direction (7).

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Stats can each be raised, but each one has different methods for that increase. See Stats for instructions.
Your number of Mutations can be increased by spending time in radiated areas. For every 10 consecutive days that you survive in a radiated area of Intensity 6 or higher, you get one point to spend on Mutations. Your GM should decide on whether the Mutations can be bought or must be random. He also decides how many points can be stockpiled. A good stopping point is 5 accumulated points.
Pure Ones are also susceptible to radiation. So, once the GM's stockpile limit is reached, the Character is no longer "Pure" .
These rules are in addition to the radiation exposure rules found later.

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With the new die-casting rules, a " + " is bad, a " - " is good. A " - " lowers your roll by the appropriate amount, a " + " raises it. You want as low as possible.
Here is a description of the types of Attack and Defense:
Hand attacks are any attempt to Hit an opponent with a bare hand or claw, or a hand-held striking weapon (including Swords, Knives, etc.).
Aimed attacks are any attempt to Hit an opponent with any fired or thrown weapon, including bow and arrow, guns, lasers, thrown knives or spears, etc.
Mental attacks are any attempt to use, or to harm an opponent with, a mental-based Mutation (with the exception of Mental Blast, which considered Aimed).
Hand defense is a block or parry with a bare hand or hand-held item. A successful defense negates the damage. If the attack has an effect (stun, paralyze, etc.) instead of damage, the effect is reduced according to your GM's decision.
Dodge is the classic "get-me-the-Hell-out-of-the-way" move. It will negate any physical damage except area effects like grenades, bombs, etc. A Dodge takes the entire combat round. If you Dodge, you cannot then attack. If you have already attacked, you cannot then Dodge. Mutations may modify this rule.
Mental defense, if successful, will halve the effect, damage, or duration of a mental-based attack.
Now comes the order of Combat:
Decide what type of attack you will attempt (Hand, Aimed, Mental). If the GM and the circumstances allow, call the location of the strike. Then roll on or below the appropriate number on d20. A roll under the required number, after modifiers, hits. A natural 20 ALWAYS misses and a natural 1 ALWAYS hits.
Simultaneously, your opponent rolls his Defense, if he is able and chooses.
If you Hit your opponent, roll d20 again. If a natural 1 or 2 comes up, the Hit is Critical (roll on Critical Hits table below).
If you miss your opponent, roll d20 again. If a natural 19 or 20 comes up, the miss is a Fumble (roll on Fumble table below). It's that simple.
A melee round is 1 second. If a Character's DEX is 16 or over, he can make 3 attacks in 2 rounds. If it is 18 or more, two attacks per round are possible. Mental attacks are two per round. Mutations may give multiple att./rnd. Open hand attacks are at 2/rnd, but cannot be combined with any other attack. Characters may attack both Physically and Mentally each round, at +2 to the Mental attack roll.
To surprise others, roll To Hit w/ Aimed Weapons.
To avoid surprise, average the INT points over 10 for the entire party to be surprised and add to 7. That or less on a d20 means that someone in the party was not surprised.
All Weapons do a specified damage (see ), which is then modified by the Hit location. All random damage is determined on d10.
Hit locations modify damage to the character's body only, not armor or Force Fields. Hit locations can be called or rolled randomly on following table with a d6.
A character is unconscious at 1 H.P., dead at 0.
Hit Locations Table
  1. Head - ANY head shot is a Critical Hit, so roll on Critical Hits-Head table below.
  2. Chest - Add 4 pts. for penetrating damage, subtract 3 pts. for impact damage.
  3. Abdomen/Crotch - Add 3 pts.
  4. Arms - No modifier.
  5. Legs - Subtract 2 pts.
  6. No Special damage.

Critical Hits
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Roll d6 on the appropriate table to determine effects.
Note: The actual severity of the Critical damage will vary according the weapon and GM's whims.
  1. Comatose. Severe brain damage. Out of game.
  2. Comatose for 1d10 days. WILL & INT down by 4 permanently. 1 extra die damage.
  3. Dead.
  4. No special damage.
  5. Unconscious for 1d10 hours. WILL & INT down by 4 for 1d4 days.
  6. Three additional dice damage.
  1. Severe lung damage. STR, DEX, & CON down by 3 permanently.
  2. Heart punctured. Dead.
  3. No special damage.
  4. Lung damage. STR, DEX, & CON down by 3 for 2d10 days.
  5. Heart damaged. STR & CON down by 3 permanently.
  6. Major vein/artery severed. Dead in 3 rounds.
  1. Two extra dice damage.
  2. Extreme internal injuries. Dead in 1d6 hours.
  3. 3 - No special damage.
  4. Internal bleeding. STR, DEX, & CON down by 4 for 1d4 weeks.
  5. One leg severed. Additional 4 dice damage (death in 2 minutes without aid).
  6. Internal damage. STR & CON down by 3 permanently.
  1. Paralyzed from waist down permanently.
  2. Paralyzed from neck down. Out of game.
  3. No special damage.
  4. Dead.
  5. No feeling in legs permanently.
  6. No feeling in arms permanently.
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coming soon

Healing rates depend on how much damage you have sustained:
If you are at or below 25% of your total HP, you heal at 5 pts. per day of rest, 3 pts. per day w/ activity, 0 pts. per day w/ strenuous activity.
If you are between 25% and 50%, rates are 4, 2, and 0, respectively.
For 50% to 75%, 3, 1, and 1.
For 75% and up, 2 pts. per day, regardless of activity.

Armor and Force Fields
Damage points are first taken off of armor or force fields. When all points from these are gone, points are taken from Character.
A piece of armor's points are the same for all portions. Thus, 30 point armor would have 30 points each on the arms, legs, head, front torso, and back torso. For simplicity, arms and legs are not divided into upper and lower sections (although individual GM's can, by all means, play it that way).
When armor points are gone, that portion of the armor is useless, but doesn't necessarily come off (the straps might still be in place).
Force fields renew at varying rates unless the projecting unit is destroyed.

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Base Movement, when given or referred to, is the normal walking speed of the Character's race. If the Character cannot walk, it is the normal speed for his particular type of movement.
An average human has a base movement of 2. That is, he can walk 2 yards per second, or 120 yds. per minute, or a little over a mile in 15 minutes.
Slow movement is anything under a Character's base movement. It is used for searching an area, or for rough terrain.
Fast movement is 50% faster than normal. Thus, a human would move 3 yds. per second, 180 yds. per minute, or a mile in just under 10 minutes.
Running is twice as fast as normal. A human can run 4 yds. per second, 240 yds. per minute, or a mile in just over 7 minutes.
A Character can Sprint for a max of 5 minutes at 7 times the normal rate. So, a human can go 7 yds. per second, 420 yds. per minute, or a mile in just over 4 minutes. After a full 5 minute Sprint, though, the Character must rest for 5 full minutes before he can perform any action.
A party can only move a fast as its slowest member.
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The vertical height that a Character can jump is determined by dividing STR by 3. The result is how high he can get his feet off of the ground.
Let's look at Garrr again:
He needs to get out of a sinkhole that he has fallen into (remember, he's not so bright). The lip is 25 ft. above his head. Can he jump and grab the edge? Well, his STR is 19. 19 divided by 3 is 6.3. Round this to 6 and you find that he can jump only 6 ft. Since he is 9 ft. tall, he is then (for all intents and purposes) 15 ft. tall. Unless his arms are 10 feet long (which they aren't), he can't reach the edge. He is stuck until he can think of something else, and, knowing Garrr, that will be a while.
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There are two types of horizontal leaping; sprinting and standing.
The distance a Character can leap while sprinting is determined by multiplying 1/2STR (round up) by base speed.
So, Garrr, needs to leap across a 30 ft. chasm to get away from a mob of murderous mutant samurai bunny rabbits. Can he do it? Well, he has a STR of 19 and a base speed of 4. 19/2 is 9.5 (round to 10). Multiplied by 4 is 40 ft. that he can jump while sprinting. This time, he manages to get out of one of his dilemmas.
A standing leap is half of the sprinting leap distance.
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A Character takes damage if he intentionally drops more than twice the height he can jump.
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A Character takes damage for falling from twice his body height or more.
For calculation purposes, a die is a 6-sided die.
Poison and Radiation
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Poisons and radiation have effects or do damage based on their level of Intensity.
Poison Radiation
Level Effect Effect
1 Just don't feel good No Effect
2 1 pt. damage No Effect
3 2 pts. damage Sick 1 day, 1% chance of random Mutation
4 3 pts. damage Sick 2 days, 3% chance of random Mutation
5 5 pts. damage Sick 3 days, 5% chance of random Mutation
6 1 die damage Sick 4 days, 10% chance of random Mutation
7 2 dice damage Sick 5 days, 15% chance of random Mutation
8 3 dice damage Sick 1 week, 20% chance of random Mutation
9 4 dice damage Sick 2 weeks, 25% chance of random Mutation
10 5 dice damage Sick 3 weeks, 1 die damage/day for 2 days, 30% chance of random Mutation
11 5 dice damage Sick 1 month, 2 dice/day for 2 days, 35% chance of random Mutation
12 5 dice damage Sick 2 months, 2 dice/day for 3 days, 40% chance of random Mutation
13 5 dice damage Sick 3 months, 3 dice/day for 4 days, 50% chance of random Mutation
14 6 dice damage Death in 6 months. 2 dice damage/day for 3 days
15 6 dice damage Death in 5 months. 3 dice/day for 4 days
16 7 dice damage Death in 4 months. 2 dice/day for 2 days
17 Death in one day Death in 3 months
18 Death in 6 hours Death in 2 weeks
19 Death in 2 hours Death in 1 week
20 Death in 1 hour Death in 1 week
If the Character's CON is greater than the level of Intensity, the effect is halved. If the CON is twice or more the level, there is no effect. This must be taken into account when figuring out gained Mutation Points.
Sickness brought on by radiation will rob character of 2 points from all Stats (except HP) for the duration of the sickness.

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Unless a Character acquires an artifact from someone willing and able to explain how it works, or the Character had previously used an artifact just like the one discovered, the Character will not know how to use one newly acquired.
To discover how to use an unfamiliar artifact, one of the Artifact Examination Charts in GAMMA WORLD First Edition should be used.
First, your GM must determine the Complexity of the item. Complexity is both a function of the Tech level of the item and the number of operations or actions necessary to use the item properly.
Complexity Ratings: Item with a Complexity Rating of A, B, or C should use Chart A. Ratings of D, E, F, and G should use Chart B. Ratings of H, J, or K should use Chart C.
There is also a large difference between learning how to use an artifact and really understanding it well enough to maintain and attempt repairs on it. Understanding takes time, patience, and practice.
To use the Artifact Examination Charts, a d10 will be used. Starting in the circle marked Start (where else?), roll the die and add or subtract any modifiers the Character may have. Anything below 1 should be counted as 1, anything above 10 should be counted as 10. Once the score is determined, follow the arrow leading to the next space indicated.
Success is gained when the last box is reached.
Each roll of the die is equivalent to 5 minutes of game time. If the players tire of their efforts, the GM may note how far they progressed. Then, the next time the players decide to try again, he should start them one step back from that stopping point.
When the skull & crossbones is landed on, the item has managed to hurt one of the Characters in some manner. It is the GM's decision as to what kind of damage is suffered, and how much.
After one hour of game time has been spent attempting to figure an artifact out, and the Character has not made any appreciable headway, the GM should inform the Character to give up.

This document contains material supported (Yeah, right!) by and owned by TSR. No claim of ownership is made on this page. I just improved it.
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