The game centers on the titular Abe, a Mudokon slave working at the RuptureFarms meat processing factory on Oddworld. When he discovers that he and his friends face death at the hands of their desperate master, he decides to escape and aid as many enslaved Mudokons as he can along the way. The player assumes the role of Abe, and must escape from the factory before embarking on a perilous quest to restore his once noble people.
Abe's Oddysee was widely acclaimed for having innovative gameplay, good graphics and engaging cut-scenes; however, its large learning curve and system of saving only at checkpoints received criticism.
The game features no user interface or heads-up display. Information is conveyed to the player in a number of ways; through instructive screens that can be activated by the player character, through scrolling messages in the background, or through groups of fireflies that can arrange themselves to produce words should the player character chant near them. No characters in the game have hit points; instead, being attacked (such as being shot or mauled) causes instant death. However, the player has unlimited lives, and upon death will re-spawn at the beginning of the level.
While the focus of the gameplay is surmounting screens, there is a secondary focus on rescuing enslaved Mudokons. GameSpeak is a pivotal ability in this respect; at the press of a button, the player character will utter short phrases that can be used to control allied non-player characters—to pull extra levers, to follow the player character, to attack enemy characters in the current screen, or simply to wait.
Possession is the player character's ability to take control of Sligs in the same screen by chanting. Possessing Sligs is a necessity in certain situations, usually to kill other enemy Sligs in the nearby screens or to give commands to nearby Slogs. However, when possessing a Slig, the player character remains immobile and vulnerable to attack. Upon abandoning control of a possessed Slig, the victim will burst into pieces.
Slave Mudokons are rescued through Bird Portals. If the player character chants when in the same screen as a Bird Portal, and other Mudokons are nearby, the portal will activate and Mudokons will run through it, disappearing. Rescuing Mudokons is not crucial to playing the game; however, rescuing at least fifty is necessary to get the good ending, and many secret areas revolve around rescuing one or two Mudokons in particularly complex situations.
At certain points late in the game, the player can gain the ability to turn into the Shrykull, a Mudokon supernatural demigod. This is usually earned by sending a certain number of Mudokons through a bird portal at once, denoted by a number circulating with the birds. With the ability, the player can, once, go into a screen with enemies or explosives, chant, turn into the Shrykull, and vaporize everything on the screen. Afterward, he turns back into Mudokon form. Achieving the ability and doing such is necessary to get past certain points in the game. The player can only turn into the Shrykull once each time they earn it, so where and when they choose to use it is important.
The purpose-created game engine and artificial intelligence for Abe's Oddysee is called A.L.I.V.E. (Aware Lifeforms In a Virtual Environment), and has been acclaimed for its realistic encounters and intelligent enemies.
Enemies in the game primarily consist of Sligs, semi-robotic creatures armed with automatic shotguns. Sligs can be possessed by the player character, who can then control the Slig and utilize its weapon. Sligs cannot see in dark shadows, which prove to create natural hiding places. Often accompanying Sligs are Slogs. Slogs are bipedal dog-like creatures that, as with the Sligs, chase and attack the player character on sight. Slogs can be commanded by Sligs when possessed by the player, and can be ordered to attack and kill others. When encountered alone, Slogs can be distracted with chunks of meat.
Glukkons also feature as antagonists. Glukkons are tall-foreheaded, humanoid creatures who are ruthless, malevolent businessmen and capitalists. They walk on their arms as they have feet upon their chest, that is why they look like they have no arms. They are the owners and bosses of RuptureFarms and the masters of the Mudokon and Slig slaves. Glukkons don't really feature in the game proper. Only in pre-rendered cut scenes, wherein they are crucial to the plot, except for the final screen of the game in which the player drops into the boardroom and vaporizes them by turning into the Shrykull.
Animals and wildlife consist of the Scrabs; carnivorous, predators that primarily live in the desert regions. Scrabs are highly territorial and attack and chase any other life form upon sight. Should they engage another Scrab, a short fight ensues in which one is killed; and Paramites, pack hunters that live in dark caves within the forest regions. When encountered individually, Paramites are shy and will flee (though if cornered they will lash out and attack). When confronted in number, however, the player character ceases to threaten them and they will immediately chase and attempt to attack. Paramites can be distracted with chunks of meat.
The primary antagonist of the game is the ruthless chief executive officer of RuptureFarms, Molluck the Glukkon. Reportedly attractive by Glukkon standards, Molluck is completely obsessed with success, doing anything within his power and cunning to achieve evermore wealth. Despite this, Molluck's business empire is failing due to declining wildlife populations; desperate, Molluck decides to use his Mudokon slave population in his food products to offset the quickly declining profits.
RuptureFarms is undergoing difficulties: the ingredients of their three major products are quickly running out, with the Meeches already extinct. While working late one night, Abe chances upon the Board Room, where the various Glukkons are discussing their dilemma. After reviewing the situation, Molluck announces his plan to use the Mudokon slaves as new meat products called "Mudokon Pops!", frightening Abe into a resolution of escaping from the factory.
Abe proceeds to elude the authorities and escape from RuptureFarms proper; immediately out, Abe sees a large moon in the sky, with its face in the shape of a Mudokon handprint, signifying the Mudokons as the "chosen people". Abe suddenly falls down a cliff, hitting his head; as he lies on the ground, BigFace appears before him in a vision.
BigFace sends Abe towards his quest: to rescue his enslaved brethren and "restore the lost land". However, he cannot accomplish this feat without first completing the spiritual trials of the Monsaic Lines and Mudokon temples. Abe journeys into the Monsaic Lines, from where he travels to the forests of Paramonia and the deserts of Scrabania. In each land, Abe completes the tests of the respective temple; after each one, BigFace gives Abe hand scars, one representing the Paramites and one representing the Scrabs.
Once Abe has both scars, he can become the Shrykull, a mystical and all-powerful demigod creature. The Shrykull stands outside life as a dualistic god, of creation and destruction, and of fear and love. With this divine power, Abe returns to RuptureFarms, rescues his Mudokon brethren and comes close to shutting it down entirely.
However, Abe is surprised, captured and bound so he cannot chant to invoke the Shrykull. It is at this point that he first appears in captivity at the start of the game. As Molluck enters the prison cell and prepares to drop him into a meat grinder, BigFace holds a meeting with freed Mudokons at the Monsaic Sanctum.
The game saw its first release on the PlayStation, DOS and Windows on September 19, 1997, on a day dubbed as "Odd Friday" by the developer and publisher; over 500,000 units were originally released worldwide. The Japanese version followed in October.
The game's audio was often singled out for praise. GameSpot gave the music a score of nine out of ten.
Most criticism toward the game was directed at the save system. Edge said that "Oddworld demands a certain level of commitment to progress", while Science Fiction Weekly claimed the game's "innovative game play makes for a steep learning curve. This initial difficulty in figuring out how to play is aggravated by a save feature that often forces players to redo difficult sections." PC Zone stated that "progress does seem to rely on trial and error, which involves much replaying of levels and gnashing of teeth. All this can be frustrating at times, especially when Abe is plonked right back at the start of a level when he dies". The game's follow-up, Abe's Exoddus, notably implemented a suspend save feature that did not require the reaching of checkpoints.
Despite this criticism, the game won many awards, including the Nobel Prize from PC Computing Magazine in December 1997, E3 Showstopper 1997 from GamePro in August 1997 and the award for Best Director from the World Animation Festival in 1997.
Oddworld Inhabitants made the altered designs a permanent feature; subsequent versions of Abe's Oddysee released outside Japan included both the changed packaging and changed Mudokon hand. Future games and media also recognise these changes as canon, although Abe's Exoddus oddly features four-fingered Mudokon sprites, and scenes from Abe's Oddysee shown in the game were not altered.