A former member of the Lin Kuei clan and a longtime friend of younger Sub-Zero, Smoke debuted in Mortal Kombat II as a hidden character to fight against. He was often spotted in the Living Forest stage in which he (along with Jade) peeked out of the trees. Like Reptile when he made his first appearance, he was simply a grey clad version of Scorpion who moved extremely fast, with puffs of smoke surrounding his body. He would appear randomly before matches, offering clues that would enable the player to fight him, as Reptile had in the original Mortal Kombat. In the official Mortal Kombat II comic by John Tobias, Smoke was revealed to be a Lin Kuei warrior, and the clan itself was depicted as becoming a high-tech organization.

Formerly a human ninja and member of the Japanese ninja clan Shirai Ryu, Scorpion is now a black and yellow garbed, hell-spawned revenant, inexorably seeking vengeance against those responsible for the destruction of his clan and the death of his family. Despite the fact that Scorpion has previously allied himself with the forces of evil (when promised either a means of resurrection on Earth or the chance to inflict his wrath against those who butchered his clan), he is not inherently evil.

Liu Kang is a Chinese Shaolin fighting monk. He moves quickly and possesses formidable fighting skills. Throughout the series, Liu Kang has been gradually portrayed as the main hero, becoming Champion after the first Mortal Kombat tournament and then following whatever quest Raiden has in mind for him. His romantic interest is Princess Kitana, but he is unable to commit himself to a relationship due to his duty (protecting Earthrealm as the Champion of Mortal Kombat) while Kitana has to stay in Edenia as reigning princess.

Reptile is a green garbed, human-like reptilian ninja that embodies the archetype of the unhappy underling. Reptile is said to be physically hideous and repulsive, but he is renowned for his great stealth and unquestioning loyalty. Unlike many other henchmen of the lords he has served, Reptile does not strive for power. Rather, he is caught in a delusional state of mind, an obsession about finding the last remaining member of his race, the Saurians, or freeing his homeworld from Outworld's grasp. This obsession is so important to him that it causes temporary fits of insanity.

There are in fact two Sub-Zeros: one older and one younger. Both are blue garbed warriors that descended from Cryomancers, an Outworld race possessing the ability to generate and control the powers of ice, although both of them were born in Earthrealm. The younger one bears a conspicuous scar on his right eye, however, as of Deception the scar has faded away, though in the game Shaolin Monks the scar is caused by Kung Lao. The Elder Sub-Zero appeared in the first Mortal Kombat; after being killed by Scorpion, his younger brother replaced him for the rest of the games. The elder brother later became the undead Netherealm wraith, Noob Saibot.