You have been chosen to represent Earth in Mortal Kombat. Be warned. Although your souls are protected against Shao Kahn's evil; your lives are not. I cannot interfere any longer as your Earth is now ruled by the Outworld Gods.
These are the words of Raiden.
For centuries Earth has used Mortal Kombat to defend itself against the Outworld's Emeperor Shao Kahn. But, Kahn becomes frustrated by failed attempts at taking Earth through tournament battle. He enacts a plan which began 10,000 years ago.
During this time Kahn had a Queen. Her name was Sindel and her young death was unexpected. Kahn's Shadow priests, lead by Shang Tsung, make it so Sindel's spirit would someday be reborn: Not on the Outworld but on the Earth Realm itself.
This unholy act gives Shao Kahn to step through the dimensional gates and reclaim his Queen. Thus enabling him to finally seize the Earth Realm.
Upon breaching the portal into Earth, Shao Kahn slowly transforms the planet into a part of the Outworld itself.
Kahn strips the Earth of all human life: Claiming every soul as his own.
But there are souls which Kahn cannot take. These souls belong to the warriors chosen to represent Earth in a new Mortal Kombat.
The remaining humans are scattered through out the planet. Shao Kahn sends an army of fierce Outworld warriors to find and eliminate them.
After the first tournament Sonya Blade turned up missing. Jax then embarked on a rescue mission into the Outworld. He found Sonya being held captive with her nemesis Kano. In freeing Sonya, Jax also frees Kano. Kano then uses the chance to escape arrest.
The ultimate advancement in Lin Kuei technology comes with the creation of the first cyber-assasin. They begin converting their human ninjas into soulless machines. But Sub-Zero refuses to take part and is marked for death by his own clan.
After winning the first Mortal Kombat and escaping from the Outworld, Liu Kang looks to the future. He begins training a new generation of shaolin alongside Kung Lao. But nothing could prepare them for the unexpected Outworld invasion.