Gamma World is a post-apocalyptic science fantasy role-playing game in which player characters explore Earth centuries after the collapse of civilization, searching for artifacts from the time before "The Great Upheaval". The game was originally designed by James M. Ward and Gary Jaquet, and first published by TSR in 1978. It borrows heavily from Ward's earlier role-playing game, Metamorphosis Alpha.
Setting Gamma World takes place in the mid-25th century, more than a century after a second nuclear war had destroyed human civilization. This war is only vaguely described in most editions of the game, and what details are provided change from version to version:
The first two editions explained that ever-increasing material prosperity and leisure had led to ever-more radical and violent social movements, culminating in a final war in the years AD 2309–2322, and ascribe the final annihilation to a terrorist group called "The Apocalypse" and the ensuing retaliation by surviving factions.
Later versions would alter the reason for the collapse. The 2000 Alternity edition explained this as having been caused by the arrival of aliens and a nuclear response. The 2003 d20 Modern iteration explained collapse as due to uncontrolled nanotechnology and artificial intelligence. The 2010 edition attributes the destruction of civilization to the activation of the Large Hadron Collider, which caused multiple realities to exchange features in an event known as the Big Mistake.
All backstories agree that the cataclysm destroyed all government and society beyond a village scale, plunging the world into a Dark Age. In many editions of the game, technology is at best quasi-medieval (in the first edition, the crossbow is described as "the ultimate weapon" for most Gamma World societies). Some, such as the 2003 and, to a lesser degree, the 2010 edition, feature advanced technology that is well known and often easily available. In contrast, super-science artifacts in earlier editions were risky to use due to the average Gamma World character not knowing how to properly operate such devices, or possibly even what the device is at all. The post-apocalyptic inhabitants of Earth now refer to their planet as "Gamma World", or, in later editions, "Gamma Terra".
The setting is chaotic and dangerous and little resembles pre-apocalyptic Earth. The weapons unleashed during the final war were strong enough to alter coastlines, level cities, and leave large areas of land lethally radioactive. These future weapons bathed the surviving life of Earth in unspecified forms of radiation and biochemical agents, producing widespread, permanent mutations among humans, animals, and plants. This has caused mutations such as additional limbs, super-strength, and psychic powers. (Random tables of such improbable mutations are a hallmark of every edition of Gamma World.) Many animals and plants are sentient, semi-civilized species competing with surviving humans. Both humans and non-humans have lost most knowledge of the pre-war humans, whom Gamma World's inhabitants call "the Ancients". The only group with significant knowledge of the Ancients are isolated robots and other AIs that survived the war. These machines tend to be damaged, in ill repair, and/or hostile to organic beings.
Player characters include unmutated humans (referred to as "Pure Strain Humans" in most editions), mutated humans, sentient animals or plants, and androids. Characters explore ruins and strange post-apocalyptic societies to gain knowledge of the Ancients and social status for themselves. Common adventure themes involve protecting fragile post-apocalypse societies, retrieving such Ancient "artifacts" as power armor, laser pistols, and anti-grav sleds, or mere survival against the multifarious dangers of the future such as gun-toting mutant rabbits, death machines, and other, more hostile, Gamma Worlders.
A recurrent source of conflict on Gamma World is the rivalry among the Cryptic Alliances, semi-secret societies whose ideological agendas, sometimes monomaniacal ones, often bring them into conflict with the rest of the Gamma World. The Pure Strain Humans' Knights of Genetic Purity, for example, wish for genocide on mutants, while Iron Society seeks the same for baseline humans. Other rivalries involve attitudes towards Ancient technology. The Restorationists seek to rebuild Ancient society while others, the Seekers, wish to destroy it.
System
Throughout the game's editions, Gamma World has been compatible with the then-current edition of Dungeons & Dragons (D&D). Attribute generation is the same, with a range of 3 to 18, randomly generated by rolling three six-sided dice. The attributes themselves are the same, but with occasional name changes such as Physical Strength instead of Strength and Mental Strength instead of Wisdom.
Character generation is mostly random, and features one of the game's most distinctive mechanics, the mutation tables. Players who choose to play mutants roll dice to randomly determine their characters' mutations. All versions of Gamma World eschew a realistic portrayal of genetic mutation to one degree or another, instead giving characters fantastic abilities like psychic powers, laser beams, force fields, life draining and others. Other mutations are extensions or extremes of naturally existing features transposed from different species, such as electrical generation, infravision, quills, extra limbs, dual brains, carapaces, gills, etc. These were offset with defects that also ranged from the fantastical—such as skin that dissolves in water, or a scent that attracts monsters—to the mundane, such as seizures, madness and phobias.
Characters in most versions of Gamma World earn experience points during their adventures, which cause the character's rank (in some editions, revel) to increase. Unlike D&D, however, the first two editions of Gamma World do not use the concept of true level or character class, and increases in rank do not affect the character's skills or combat abilities. In the first three editions of the game, character rank is primarily a measure of the character's social prestige.
The game mechanics used for resolving character actions vary between Gamma World editions. In the first two editions, use matrix-based mechanics, where two factors (one representing the actor or attacker, and one representing the opponent) are cross-referenced on a chart. For actions, such as attacks, the number located on the matrix represents a number the acting player must roll. For other actions (such as determining the result of radiation exposure), the matrix result indicates a non-negotiable result.
The third edition rules replaced specialized matrices with the Action Control Table (ACT), a single, color-coded chart that allowed players to determine whether a character action succeeded, and the degree of success, with a single roll. The ACT requires the referee to cross-reference the difficulty of a character action with the ability score used to complete that action, determining which column of the ACT is used for that action. The character's player then rolls percentile dice; the result is compared to appropriate column, determining a degree of success or failure and eliminating the need for second result roll (e.g. the damage roll that many games require after a successful combat action).
The fourth edition was directly compatible with second edition AD&D with some minor differences in mechanics. The fifth and sixth editions make the game a campaign Setting and require the core books to play. The fifth edition uses the Alternity system which is mostly represented in the book but required the core rules in order to resolve some factors. The sixth edition required the d20 Modern rulebook in order to play the game.
The seventh version uses a streamlined version of Dungeons & Dragons 4th edition mechanics. Character generation choice though was nearly fully removed. Instead of choosing a character class, a player had to roll a twenty-sided die two times and consult an accompanying character origin table. For example, a player might obtain the result "Radioactive Yeti" and gain the powers associated with the "Radioactive" and "Yeti" origins. Attributes, mutations, and skills were also randomly assigned. Two decks of cards comprising the core of a Collectible Card Game are included with the game. One deck represented random Alpha Mutations, which could be drawn to gain temporary powers, and the other contained various Omega Tech, powerful technological devices that could possibly backfire on those that used them. Some fourth edition rules enhancements for the setting include new damage types such as "Radiation", Gamma World-specific skills, and increased lethality. Despite these differences, it is possible to use characters and monsters from a D&D game in Gamma World and vice versa.
History First edition (1978) The original Gamma World boxed set (containing a 56-page rulebook, a map of a devastated North America, and dice) was released in 1978. TSR published three accessories for the first edition of the game:
GW1, Legion of Gold by Gary Gygax, with Luke Gygax, and Paul Reiche III GW2, Famine In Far-Go by Michael Price Gamma World Referee's Screen
Grenadier Miniatures supported the game, with a line of licensed miniatures.
At least one other TSR product was announced -- Metamorphosis Alpha to Omega, an adaptation of Metamorphosis Alpha's campaign setting to Gamma World's rules . Work on the adaptation was halted when a 2nd edition of Gamma World was announced. This was later released as Metamorphosis Alpha to Omega using the Amazing Engine rules.
Second edition (1983) The second edition Gamma World boxed set (with rules designed by Ward, Jaquet, and David James Ritchie) was released in 1983. Two modules and two accessories were released for this version:
GW3, The Cleansing War of Garik Blackhand by Michael Pierre Price and Garry Spiegle GW4, The Mind Masters by Philip Taterczynski GWAC1, Gamma World Referee's Screen and Mini-Module GWAC2, Gamma World Character Sheets
TSR also produced four packs of Gamma World miniatures. TSR started production on a third adventure module, which was to be assigned the identification code GW5 and had the working title Rapture of the Deep. This module was not published. However, a 'ghost' Second Edition GW5 Rapture of the Deep module was produced in 2007.
Third edition (1986) The third edition of Gamma World was a boxed set, credited to James M. Ward. This version of the rules became notorious for the number of editorial mistakes, including cross-references to rules that didn't appear in the boxed set. The errors were serious enough that TSR published a Gamma World Rules Supplement containing the "missing" rules. The Rules Supplement was sent to gamers who requested it by mail, and included in reprintings of the boxed set.
The five modules TSR published for Gamma World's third edition introduced the setting's first multi-module metaplot, which involved rebuilding an ancient 'sky chariot':
GW6, Alpha Factor by Kim Eastland GW7, Beta Principle by Bruce Nesmith GW8, Gamma Base by Kim Eastland GW9, Delta Fragment by Kim Eastland GW10, Epsilon Cyborgs by Kim Eastland
TSR stopped publishing the third edition before the multi-module storyline could be completed. In 2003 an unofficial conclusion to the series was published under the title GW11 Omega Project.
Despite its editorial issues, the third edition rules were well-received enough to win the 1986/1987 Gamer's Choice Award for "Best Science-Fiction Roleplaying Game".
Scott Taylor of Black Gate in 2015 rated the GW6-GW10 series as #7 in The Top 10 Campaign Adventure Module Series of All Time, saying "if you are ever in the mood to crack out Gamma World, or just have a great campaign setting for any post-apocalyptic campaign, this super series could be for you."
Fourth edition (1992)