Ultratech is a very powerful megacorporation (entities which, in this future setting, replaced all governments) which organizes a tournament called Killer Instinct. Along with regular participants, experimental creatures created by Ultratech also fight in the tournament. Ultratech also discovers a technology to make bridges between dimensions, and to also release from this dimensional prison a two-headed monster called Eyedol, an ancient warrior that was locked away along with his rival.
- B. Orchid: The main protagonist of the game and also the only female character. Orchid is a very sexy secret agent in a green latex outfit armed with two lightsabers. Her mission is to shut down the criminal syndicate Ultratech. Her full name is Black Orchid. She has 2 fatalities. One where she gives the opponent a heart attack by unzipping her latex outfit and flashing her boobs, and the other where she turns the opponent into a frog (and at the player's option, she stomps on them). Her stage is a rooftop in a big city.
- Jago: A Tibetan Monk following the tiger spirit. Like Orchid, his mission is to destroy the evil within Ultratech. He has 2 fatalities. One where he meditates and a car falls down on the opponent, and the other where he stabs the enemy with his katana. His stage is the shrine Jago worships the tiger spirit.
- Chief Thunder: A native American Indian armed with 2 tomahawks. He entered the tournament to find out what happened to his missing brother Eagle, who was in last year's tournament. He has 2 fatalities. One where he rain-dances and summons a bolt of lightning onto the opponent, and other where he sends the opponent flying with his tomohawk, leaving various objects behind. His stage is an old bridge in a canyon.
- TJ Combo: A former heavyweight boxing champion. He was stripped off his title and kicked out of the circuit when it had been discovered that he had cybernetic implants in his arms. Ultratech promises him to return his title if he wins the tournament. He has two fatalities. One where he breaks the opponent's neck, and the other where he punches the opponent on the screen. His stage is a boxing gym.
- Glacius: An icy alien from another planet who was kidnapped by Ultratech, but was promised to be released and returned home if he wins the tournament. He has three fatalities. The first one is where he turns into a gel-like mass and absorbs the foe (arcade only), the second where he turns into a puddle of acid which the foe melts into, and the third where he injects the foe with a substance that turns them to ice. His stage is an arctic temple.
- Cinder: He was a convict that was chosen for an experiment, only to find out that his body turned to living flame, but was promised to change back if is able to defeat Glacius in the tournament. His real name is Ben Ferris. He has two fatalities. One where he creates a pool of lava, which the foe melts into, the other where he shoots flames and reduces the foe to a pile of ashes. His stage is a rooftop of an ancient warehouse in a desert.
- Sabrewulf: Count Von Sabrewulf is a werewolf, and is promised a cure if he wins the tournament. He has two fatalities. One where he stabs the foe with his enlarged claws, the second where he slams the foe onto the screen. His stage is a chateau in a large mansion.
- Riptor: A dinosaur created as an experiment by Ultratech. The tournament serves to test its abilities. It has three fatalities. The first one, it eats the opponent, The second it spits acid onto the foe, and the third it stabs the foe with its tail. Its stage is an altar with marble flooring.
- Spinal: A skeleton that was once a viking warrior. After his death, he lost some of his memories, and serves Ultratech in order to return them. He has two fatalities. One where he summons one of his skeleton friends and drags the opponent to Hell (SNES version: summons lightning and reduces the foe to ashes). The second where he stabs the opponent with the spike on his shield. His stage is a rooftop of a haunted castle.
- Fulgore: A robot created by Ultratech. If it can prove its master capabilities, mass production will begin. It has two fatalities, one where it replaces its head with a machine gun and shoots the opponent, the other where it shoots a laser at the opponent. Its stage is a factory where it was built.
- Eyedol: An ancient warlord with two heads. He is the final boss of the game. He was trapped in a dimensional prison in the distant past. Ultratech released him to be the final combatant in the tournament. It is confirmed that he and Gargos were rivals. Ironically, he has no fatalities, but he's incredibly powerful.