Stepping fresh into a new Mortal Kombat game can be a confusing experience. There are ninjas, cyber ninjas, undead, and whatever Goro is. Also Freddy Krueger was there once. The upcoming Mortal Kombat 11 looks really cool, but it also confuses things further by mixing the current story with the classic versions of the characters popularized in the '90s. To get you ready for the crisscrossed timelines of MK11, here's a refresher on all the important stuff.
2011's Mortal Kombat Was A Reboot
2011's Mortal Kombat was the ninth game in the main series, but took things back to the beginning. That's because the good guys lost the Battle of Armageddon, the fight to decide the fate of all realms. Raiden is the only force of good left, and he faces Shao Kahn. Kahn is powered up, leaving Raiden outmatched. The only hope he has is to send a message to his past self. He does, bringing us players back to the first game's Mortal Kombat tournament.
The original Mortal Kombat starts off much like the first. Liu Kang, Johnny Cage, and Sonya Blade all end up allying with Raiden to defeat the evil sorcerer Shang Tsung. However, Raiden is now driven by a different goal as his future self sent him the warning that "he must win." This causes him to put more faith in Liu Kang, who is is the last Earthrealm participant left in the tournament. It also causes Raiden to try to put a stop to the various rivalries among the kombatants, such as Sub-Zero and Scorpion, but he often fails.
Liu Kang wins the tournament as he did in the original timeline, and this is where things start to diverge. Shang Tsung returns after his defeat, proposing one last tournament to end it all. Whichever side wins will win forever, putting an end to the regular cycle of Mortal Kombat tournaments that endanger the Earthrealm. Raiden has a problem with this, as his visions of a doomed future are still happening. He concludes that Liu Kang is not the "he" that must win, and so leaves him behind. He takes Johnny Cage and Jax to Outworld to represent Earth in the new tournament.
The events of the second Mortal Kombat game play out fairly normally here, with Kitana changing sides and becoming fond of Liu Kang. Raiden's team also adds Smoke and Sub-Zero to its ranks. It all culminates in a final battle against Shao Kahn. The big change here is that Raiden's insistence that Liu Kang isn't "the one" causes Kang to doubt his role in the battle. He chooses to rescue a captured Kitana, letting Kung Lao take his place as Shao Kahn's challenger. Kung Lao is killed in this battle. In a fit of rage, Liu Kang kills Shao Kahn in retaliation.
Except Shao Kahn is not actually dead. Thirsty for revenge but unable to hold another Mortal Kombat tournament due to the previous agreement, he instead plots a full scale invasion of Earthrealm. The ensuing battles kill pretty much everyone, leaving Raiden desperate and Liu Kang losing faith in the thunder god.
Things get even more heated when Raiden learns the truth behind his prophecy. The "he" who must win is actually Shao Kahn. If Shao Kahn is allowed to take Earthrealm forcefully without winning a Mortal Kombat, he would bring down the punishment of the Elder Gods. Liu Kang cannot accept this outcome and fights Raiden. A combination of Liu Kang's fire and Raiden's lightning accidentally kills Liu Kang, and Raiden surrenders to the might of Kahn.
At the final moment, the Elder Gods infuse Raiden with their powers, using him to punish Kahn for violating the rules. The powered-up Raiden defeats and destroys Kahn. Earthrealm is saved, but at the cost of most of its champions. Unfortunately, we learn that this was all orchestrated by Shinnok, a fallen Elder God. Since this new timeline has both Earthrealm and Outrealm losing its greatest fighters, it becomes a prime target for this new evil...
25 Years Later
That leads us to Mortal Kombat X, which picks up 25 years after. Shinnok's attack fails spectacularly due to Johnny Cage possessing some weird energy that makes him immune to Shinnok's magic. Cage brutally beats Shinnok and Raiden traps the evil god in an amulet. Fast forward, and Johnny is commanding his own daughter, Cassie Cage, who lacks this power, on a mission to maintain the truce Earth brokered with the Outrealm.
While the new emperor, Kotal Kahn, is willing to keep the peace, a group of rebels led by Mileena is trying to overthrow him. It also turns out that Mileena stole the amulet in which Shinook is trapped and is drawing upon his power. This threat causes the emperor to team up with Cassie Cage's group to put a stop to Mileena.
Unfortunately, Kotal betrays Cassie's team. This setup allows a servant of Quan Chi, a sorcerer who worked in the shadows during Shao Kahn's attack, to make a play for Shinnok's amulet. Quan Chi specializes in creating revenants, undead soldiers that use the souls of the deceased. Among these undead are Liu Kang and Kung Lao. However, Sonya Blade is able to capture Quan Chi and brings him to Raiden to hopefully have the revenant process undone. The plan backfires and brings about the resurrection of Shinnok.
The hero turns out to be Cassie Cage in the end, using the same energy as her father to dispel Shinnok's magic and defeat him. But, as seems to be a theme with Mortal Kombat, there is a price to this victory.
Those Who Didn't Die Went Bad
Raiden was able to weaken Shinnok by drawing away his dark energy, but it corrupted him. The epilogue sees him in a darker form. He says that Earthrealm has been weak in the past, but that it will now seek vengeance whenever it is attacked. To emphasize the point, he tosses Shinnok's severed head on the floor as an example.
With Shinnok dead, his Netherrealm is now ruled by the undead couple of Kitana and Liu Kang. Johnny Cage was last seen severely injured, suggesting Cassie will take his place as the hero of Earthrealm. They'll need her in MK11, because as we've seen, the heroes of this rebooted timeline have a habit of becoming dead or corrupted.