Mortal Kombat takes place after the events of Mortal Kombat: Armageddon, but goes back in time during the events of Mortal Kombat, Mortal Kombat II, and Mortal Kombat 3, in which the main protagonist of the game's story mode, Raiden, receives a message from himself in the future in which Shao Kahn will be the supreme ruler of all realms, and must take necessary steps to alter the timeline in order to avoid Kahn's rule.
All versions of Mortal Kombat features all 25 playable characters from the original Mortal Kombat to Ultimate Mortal Kombat 3, save for Quan Chi, who was introduced in Mortal Kombat 4. Excluding Motaro, who is killed off in the game's story mode, all major bosses from MK1 to UMK3 appear as unplayable bosses in the game, Shao Kahn, Goro, and Kintaro. The game also contains 2 playable hidden characters, Quan Chi, and Cyber Sub-Zero, as well as 4 unplayable variations of selectable characters, MK1 Reptile, MKII Smoke, MKII Noob Saibot, and MKII Jade, who all can be fought against by meeting certain requirements in the game. NetherRealm Studios, the developers of MK, have confirmed that Kenshi, a blind swordsman introduced in Mortal Kombat: Deadly Alliance, Skarlet, who was a rumored character in MKII, Rain, and Freddy Krueger from Nightmare on Elm Street will be the four DLC characters.
In addition to the character roster in the game, the PS3 version of the game adds Kratos from God of War in the roster as an exclusive character. The Xbox 360 version does not have an exclusive character.
- Scorpion: Hanzo Hasashi was once a member of the Japanese Shirai Ryu ninja clan. Given the name Scorpion for his blindingly fast and deadly fighting skill, his life was blessed with glorious kombat in the name of his Grand Master. But when he, his family and his clan were brutally exterminated by Sub-Zero and the Lin Kuei, Scorpion's existence became eternal torment. Resurrected by the malevolent necromancer Quan Chi, he entered the Mortal Kombat tournament to slay Sub-Zero and avenge the murders of his kin.
- Liu Kang: Orphaned at a very young age, Liu Kang was raised by Shaolin monks, who taught him the way of the spiritual warrior. They soon recognized his potential as a contender for the Mortal Kombat tournament and rigorously trained him for this task. Raiden, too, understood that Liu Kang was Earthrealm's best hope for freedom and introduced him to Master Bo' Rai Cho to further his development. Once fully trained, Liu Kang bested all challengers and earned the high honor of representing the Shaolin in the Mortal Kombat tournament. He and Raiden then embarked on their fateful journey to Shang Tsung's island to compete in this pivotal kontest.
- Kung Lao: Kung Lao's ancestor was defeated by Goro 500 years ago in the pivotal match that saw Shang Tsung attain control of the Mortal Kombat tournament. To him this contest is about more than Earthrealm's freedom. His life's goal has been to slay Goro and win the tournament, thus restoring his family's honor. After being defeated by Liu Kang in a qualifying bout, he disguised himself as one of Shang Tsung's guards to gain admittance. Kung Lao believes he is ready for the challenge. The time to avenge his ancestor is at hand.
- Sub-Zero: An assassin of the Lin Kuei clan, Kuai Liang commands the power of ice and cold. Unlike other members of his clan, he and his older brother, Bi-Han, were abducted as children by the Lin Kuei and trained in the techniques of assassination throughout their lives. Though his codename is Tundra, he has now assumed the mantle of Sub-Zero to honor his brother after Bi-Han's mysterious death. With the help of his fellow Lin Kuei Smoke, Sub-Zero tirelessly hunts the one who killed his brother.
- Sindel: The mother of Kitana, Queen Sindel was forced into marriage with Shao Kahn when he conquered her realm of Edenia. In an attempt to thwart the emperor's designs on Earthrealm, she sacrificed herself. Her suicide created a magical ward preventing him from setting foot there. But now the barrier has been dissolved. Sindel has been resurrected, her mind enslaved by Shao Kahn. Earthrealm's former ally has become a deadly threat.
- Ermac: As punishment for resisting Shao Kahn’s claim to the realm of Edenia, the souls of the vanquished were torn from their bodies and fused together to form the being now known as Ermac. Bent to Shao Kahn’s will, Ermac is his foremost enforcer. The essences of so many souls bound together give Ermac immense telekinetic power–an advantage that will destroy Earthrealm’s resistance to Shao Kahn’s rule.
- Reptile: His home realm of Zaterra is gone, mysteriously destroyed ages ago. Reptile is the last known surviving member of his race. He has since made Outworld his home. Shao Kahn has made use of Reptile’s mastery of stealth to spy on suspected traitors and slay known enemies of the empire. But the knowledge that he is the last of his kind gnaws at Reptile. He would give anything, destroy anyone, if it would bring his realm back from the abyss. Self-pity fuels his aggression as he inflicts suffering and death on others.
- Kitana: Over 10,000 years old, Princess Kitana remembers little of her early years. Her mother, Queen Sindel, died mysteriously ages ago in Earthrealm. Most of her life she has loyally served her father, Shao Kahn, in his unending quest to conquer the realms. With her closest friend, Jade, Kitana enforces his brutal will. But there is a feeling tugging at her... a feeling that the life she has known is a deception. For the moment, Kitana dutifully works to ensure Outworld's victory in this latest Mortal Kombat tournament. If she were to lower her guard, however, she might discover that her Earthrealm opponents can lead her to answers.
- Johnny Cage: There is no greater martial arts movie star than Johnny Cage. Films such as "Dragon Fist", "Time Smashers" and "Citizen Cage" have made him one of the most highly paid actors in Hollywood. But there is more to Johnny than even he knows. He is a descendant of an ancient Mediterranean cult who bred warriors for the gods -- warriors who possessed power beyond that of mortals. This legacy has made Johnny Cage a star. More important, it will aid him in the battle to come.
- Jade: An assassin for Shao Kahn, Jade has earned a reputation as an agile and stealthy warrior. Her family was Edenian nobility and served the emperor once he conquered their realm, giving Jade to him as tribute when she was a child. After years of rigorous training in the art of kombat, Shao Kahn awarded her the position of Bodyguard to Princess Kitana. Over the centuries she and Kitana have become close friends, which makes Jade's secret orders from Shao Kahn painful to accept: Should Kitana's loyalty falter, Jade must kill her friend.
- Mileena: Shang Tsung has created many abominable creatures in his Flesh Pits, but none so twisted as Mileena. A fusion of Edenian flesh and Tarkatan blood, Mileena is both beauty and beast. This dichotomy has made her mind unstable; she is prone to fits of madness and savagery. Though she has the appearance of a mature woman, she is more child than adult--a blank slate conformed to Shao Kahn's will. Devoid of conscience or remorse, Mileena will butcher anyone to appease her beloved father.
- Nightwolf: Nightwolf is one of few Earthrealm mortals with a strong connection to the spirit world. A powerful Native American shaman, he is guided by the empyrean forces and communes with divine beings such as Haokah, known to the East as Raiden. Nightwolf's devotion allows the Spirits to work through him, granting him unnatural long life and ethereal weapons to kombat the darkness that threatens mortal-kind. In the coming crisis, however, it is not Nightwolf's arsenal that will alter fate. His faith in the Spirits will inspire those who have lost hope.
- Cyrax: A skilled Motswana warrior, Cyrax relies on his natural fighting ability, his chi, to carry out Lin Kuei missions. He is proud to serve, but when the Grand Master initiates a program to convert the clan into cyborgs, Cyrax resists. He is reluctant to lose his humanity, which he believes is more effective than any mechanical augmentation. He has contemplated leaving the clan, fearing that it is no longer an organization of honorable assassins. Cyrax knows, however, that such a decision means death at the hands of his former comrades. No one leaves the Lin Kuei.
- Noob Saibot: Noob Saibot's origins are unknown, but he is likely a revenant: a fallen warrior resurrected by the Netherrealm sorcerer Quan Chi to fulfill a dark objective. Noob has been assigned to aid Shao Kahn in his acquisition of Earthrealm. A faithful servant and a recent addition to the Brotherhood of Shadow, he will obey his master, Quan Chi, and complete his mission. But he is biding his time. Noob Saibot has a dark objective of his own.
- Smoke: Originating from Prague, Tomas Vrbada was recruited by the Lin Kuei for his impressive ability to escape capture. Able to transform into a wisp of smoke, his talent has proved useful on countless missions. Smoke has no memory of his childhood. His only family is the Lin Kuei, more specifically the younger Sub-Zero, who is like a brother to him. It has been Smoke's hope that through the Lin Kuei he will discover his past--and the origin of his power.
- Sonya Blade: As a girl, Sonya idolized her father, a U.S. Marine. When he embarked on a covert operation and never returned, she vowed to honor his memory. She joined the Marines and pushed herself hard, quickly rising in rank. Sonya's impulsiveness didn't win her many friends, but her skills and loyalty gained the respect and admiration of all who fought beside her. Though she has never given up her quest to uncover the truth behind her father's disappearance, she realizes that she might never see him again. Now Sonya finds herself caught up in the mysterious Mortal Kombat tournament. Like her father, she too could become a casualty of war.
- Jax: A decorated member of the U.S. Special Forces and a formidable close- kombat warrior, Major Jackson Briggs' current mission is to bring down the notorious criminal organization known as the Black Dragon. With Lieutenant Sonya Blade, he has seized many of their weapons caches. But when a trusted informant, Kano, was revealed to be a high-ranking member of the Black Dragon, Jax made Kano's capture his priority. Kano has gotten the better of Jax thus far, leading the Special Forces into numerous deadly ambushes. Jax and Sonya finally cornered Kano on an uncharted island but were overpowered by the island's inhabitants. They have now been forced into a sadistic ritual of bloody kombat.
- Kano: Undisciplined and dangerous, Kano is a thug for hire. From weapons dealing to cold-blooded murder, his military training has made him the go-to man for the Black Dragon. But when an operation went to hell and his face horribly mutilated, Kano's crime spree was almost ended. Ever the survivor, he used his underworld connections to find a cyberneticist capable of repairing the damage. Kano was fitted with several high-tech enhancements, most notably his eye laser. With these new weapons, Kano's reign of terror has only just begun.
- Kurtis Stryker: One of New York City's Finest, Stryker is a one-man SWAT team. He was once decorated for single-handedly thwarting the terrorists in the famous Greenberg Tower Incident, and again for rescuing passengers of a speeding crosstown bus rigged to explode. He was unprepared, however, for the magical portal that spewed forth creatures from another realm--a realm he didn't even know existed. So far his kombat training has gotten him through the first wave of creatures. It'll take more than rocket-launching Tarkatans to stop this die-hard cop.
- Shang Tsung: A treacherous sorcerer who consumes the souls of his victims, Shang Tsung has played host to the last nine Mortal Kombat tournaments in Earthrealm, stacking the odds in favor of his master. Originally from Earthrealm, Shang Tsung's magical abilities led him to discover the realm of Outworld. There he fell in league with its ruler, Shao Kahn, and pledged his life to him in return for enhanced power. He is now bound to the emperor by powerful dark magic. For centuries he has submissively done Shao Kahn's bidding. Should he fail in his mission to secure Earthrealm, he will suffer the emperor's wrath.
- Baraka: Baraka is the fiercest of the Tarkatans, vicious nomadic mutants from the wastes of Outworld. Like all Tarkatan males, he joined Shao Kahn's army once he came of age and survived the brutal Ritual of Blood. He gained the rank of Enforcer after single-handedly defeating a rebel faction. His loyalty and strength make him a favorite of the emperor; his retractable blades have slain many of Shao Kahn's most bitter enemies. As a kontestant in the Mortal Kombat tournament, he will ensure his emperor's claim to Earthrealm.
- Kabal: Once a member of the Black Dragon clan, Kabal gave up his life of crime and put his fighting skills to more positive uses. He joined the New York City police force to kombat the underworld element he once served. This transition helped ease the pain of dark memories. But when New York was invaded he underwent another transformation--one that would afflict him physically. Severely injured in battle, he is doomed to wear a life support system forever.
- Raiden: Raiden is the God of Thunder and Protector of Earthrealm. Ageless and wise beyond measure, he leads Earthrealm's mortals in the endless battle against the forces of darkness. When Shao Kahn, Emperor of Outworld, threatened to merge his realm with Earthrealm, an overwhelmed Raiden implored the Elder Gods to give Earthrealm a fighting chance. Thus the Mortal Kombat tournament was created. For millennia Shao Kahn has been kept at bay, but nine consecutive losses to Goro have eroded hope that Earthrealm can be saved. Determined to prevent Armageddon, Raiden tirelessly quests to find a champion worthy of Mortal Kombat.
- Kratos: Ancient Greece knew no more bloodthirsty a warrior than Kratos, who for a time was the God of War. Mortal once more, Kratos withdrew from the ages-old clash between men and gods. But his solitude was broken when he was ripped through space and time. As the madness subsided, Kratos found himself in present-day Outworld, kneeling before Shao Kahn. To ensure his victory in Mortal Kombat, the emperor had invoked an ancient ritual, sacrificing the souls of his vanguard to summon and enslave the most powerful warrior of all time. But the spell alone could not contain Kratos, who soon regained his free will. Enraged by Shao Kahn's arrogance, Kratos vowed to rip the warlord's spine from his body. The God of War had returned to battle.
- Cyber Sub-Zero: An assassin of the Lin Kuei clan, Kuai Liang commands the power of ice and cold. Unlike other members of his clan, he and his older brother, Bi-Han, were abducted as children by the Lin Kuei and trained in the techniques of assassination throughout their lives. Though his codename is Tundra, he has now assumed the mantle of Sub-Zero to honor his brother after Bi-Han's mysterious death. With the help of his fellow Lin Kuei Smoke, Sub-Zero tirelessly hunts the one who killed his brother.
- Sheeva: Sheeva is a member of the four-armed Shokan race. Her markings reveal that she is of the royal Draco lineage. Like all Shokan, she pledged her life to Shao Kahn, bringing honor to her race by serving him. During an attack by Edenian rebels on Shao Kahn's fortress, Sheeva fiercely protected Queen Sindel and prevented her capture. She was subsequently appointed Sindel's personal bodyguard until the queen's mysterious death in Earthrealm. Sheeva is now the master jailer of Shao Kahn's oppressive dungeon
- Quan Chi: The Netherrealm has produced many vile beings, but none rival the Arch-Sorcerer Quan Chi. In lieu of Netherrealm demons, he prefers to resurrect deceased warriors for use in his sinister plans. Foremost among them is the tortured Shirai Ryu ninja Scorpion, who is Quan Chi's personal assassin. Quan Chi is building an army of such specters--the purpose of which has yet to be revealed. Another mystery is the sorcerer's involvement in the Mortal Kombat tournament. The Netherrealm has no stake in its outcome, which leads some observers to question his presence...
- Kenshi: For years the swordsman Kenshi traveled the world in search of worthy opponents. When a mysterious elderly man named Song offered to show him the location of Sento, an ancient sword worthy of his abilities, Kenshi succumbed to pride. He followed Song to a tomb wherein lay the Well of Souls. When Kenshi retrieved the sword, spirits of ancient warriors spewed forth, blinding him. Song then revealed himself to be Shang Tsung. He consumed the souls, leaving Kenshi in the dark labyrinth to die. But Sento called to Kenshi. It led him out of the tomb and revealed his lost heritage as a descendant of the warriors who had been buried there. Kenshi vowed to slay Shang Tsung and free the souls of his ancestors.
- Skarlet: Shao Kahn has many warriors under his command, but his trust lies solely in the fighters of his own creation. Warrior blood gathered from countless battlefields, fused with sorcery, produced his most effective enforcer yet: Skarlet. An expert tracker, she preys on those deemed enemies of the empire. During kombat, Skarlet gains strength from her opponent's blood, absorbing it through her skin. Shao Kahn has a new mission for this formidable kombatant: discover Quan Chi's true intentions and kill him if he plots betrayal of the emperor.
- Rain: A refugee orphaned by Shao Kahn's conquest, Rain grew up under the protection of the Edenian Resistance. An exceptional fighter, he soon rose through their ranks. As his reputation grew, so did his arrogance. When Rain demanded leadership of the Resistance forces, he was refused. Infuriated, he turned against his rebel comrades and betrayed them to their sworn enemy. In payment for this treason, Rain was promised his own army by the emperor Shao Kahn. Power would be his - no matter the cost...
- Freddy Krueger: A malevolent spirit of the Dream Realm, Freddy Krueger preys on the souls of the living as they sleep. When Shao Kahn began to steal Earthrealm's souls - souls Freddy considered his own - Freddy battled the emperor in the Dream Realm. But Shao Kahn's will was too strong. He pulled Freddy into the real world, where he was mortal, and defeated him. A badly injured yet determined Freddy fitted both his hands with demonically enhanced razor gloves. Once he has killed Shao Kahn he will find a way back to the Dream Realm, where he will torment Earthrealm's souls for eternity.
- Shao Kahn: Known for his viciousness, cruelty and intimate knowledge of the black arts, Shao Kahn strikes fear in anyone he encounters. So mighty is this Emperor of Outworld that he intimidates even the powerful Shang Tsung. Shao Kahn incorporates his incredible strength around a single purpose: to merge all the realms into Outworld. He envisions himself the tyrant ruling all that exists. And to that end, he destroys anything in his path with a lust for killing that takes the breath away from even the fiercest warrior. Emperor Shao Kahn's lust for power is matched only by his ruthlessness. Millennia ago he overthrew Onaga as ruler of Outworld and has conquered many other realms since. Eventually he turned his attention to Earthrealm. The Mortal Kombat tournament prevents him from taking the realm by force, but if Shao Kahn's champions win 10 consecutive tournaments, Earthrealm will be his. As long as his champion Shang Tsung and Prince Goro do not fail him, he will be victorious.
- Goro: Prince Goro has brought much honor to the Shokan race by serving Shao Kahn. His bloody achievements include crushed rebellions and conquered provinces. During the past 500 years he has been celebrated for winning the last nine Mortal Kombat tournaments for Outworld. Should he defeat Earthrealm's champion this time, he will become more than legendary. His victory is assured. There are none in Earthrealm who can withstand the might of Goro.
- Kintaro: Like Goro and Sheeva, Kintaro is of the four-armed Shokan race. Unlike his aristocratic comrades, however, he is of lower-class Tigrar lineage. As is customary when recruiting Shokan and Centaur into Shao Kahn's service, one of each race must face each other in bloody kombat. Kintaro killed his opponent and, in an unprecedented act of bravado, roared for more Centaur blood. Centaurs leapt furiously into the ring to their demise. This savagery led Shao Kahn to appoint Kintaro his personal bodyguard.