As the months pass, it's becoming more and more likely that Kingdom Hearts 3 is actually going to release in 2018(update: January 29, 2019. I was close!). Judging by the latest trailer, it also seems pretty likely the game's plot is going to involve some pretty deep lore cuts that even fans might not remember. That being the case I'm feeling compelled to write something, a primer of the information needed to understand what the hell is happening in what is sure to be one of the biggest games of the year. I wish to not only refresh my own memory and the memories of other long time fans, but also get up to speed any onlookers in the Giant Bomb community being dazzled by the trailers yet put off by the six entries between Kingdom Hearts 2 and Kingdom Hearts 3. Let me assure any of you reading that while Kingdom Hearts is indeed complicated and dense; is it not, as the internet would have you believe, unintelligible nonsense. I will be skipping over quite a bit, and fudging some specifics to make it easier to understand. Spoilers obviously, now let's dive in.

The Elevator Pitch

A plot summary provided by the Kingdom Hearts 3 Sora Play Arts Kai figure Packaging:

Through countless adventures across many worlds in his long battle against the darkness, Sora, once a little boy who only dreamed worlds beyond his island even existed, has grown up to a dashing young man. Now he is realizing that that battle has played out exactly as Master Xehanort had planned, and the second Keyblade War, the final struggle between light and dark, looms ahead. To counter the overwhelming darkness, Sora and his friends must gather the seven guardians of light. His best friend Riku and King Mickey seek out a battle-scarred Keyblade wielder, while Sora, Donald, and Goofy set off on a journey to find “the Key to Return Hearts.” Never-before-featured Disney worlds set the stage for another daring adventure to save the universe!

This is a very long winded and obtuse way of saying something actually pretty simple. The protagonist of this story is Sora. The villain is Xehanort. Xehanort has gathered thirteen warriors of darkness and is forcing Sora to gather seven warriors of light so the two forces can duke it out in one final conflict. The whys and hows of all this are pretty complicated and we'll get into them, but that's the gist of it. As for the Key to Return Hearts....I've not nothing. It's never been brought up before, but I'm sure we'll find out.

Sora and the Seven Warriors of Light

Sora is the hero of the series, chosen wielder of the Keyblade and all around good guy. Although, aside from defeating the bad guys most events happen to him rather than he himself propelling the plot. Due to events in Dream Drop Distance he lost all his abilities and was more or less reset to level one for the new game. He was last seen in the after credits scene of ~a fragmentary passage~ heading to Olympus Coliseum to learn about getting lost power back from someone who has experience in that area.

Riku is the rival character to Sora. He's edgy and mopey and DARK. He was the original chosen wielder of the Keyblade, but was tricked into being evil so it transferred to Sora. He's better now and has his own Keyblade, but ever since has been struggling with the darkness inside him. In the after credits scene of ~a fragmentary passage~ he discovers a woman named Aqua is trapped in the Realm of Darkness, and sets off with Mickey Mouse to try and save her.

Mickey is the King of Disney Castle as well as a Keyblade wielder. Throughout the series he has worked behind the scenes to help the heroes, only showing up for one scene at the end of Kingdom Hearts and sporadically in Kingdom Hearts 2. Now though, it seems he'll take a more active role in his journey with Riku.

Kairi was originally presented as the damsel in distress and love interest of the series, but towards the end of Kingdom Hearts 2 she obtained her own Keyblade. She is also a Princess of Heart, possessing a heart of pure light of which there are only seven in all the worlds. She was last seen in the after credits scene of ~a fragmentary passage~ heading off to see Merlin where she'll be trained along with Lea, the other new Keyblade wielder.

Lea is a former villain turned ally. Lapsed fans might know him better as Axel. You see, without getting too far into it Lea lost his humanity, becoming a Nobody (more on those later). Along with a group of others who did the same, he changed his name to an anagram with an added X. These people named themselves Organization XIII. He eventually had a change of heart and turned on his comrades, losing his life in the process. However, it turns out when a Nobody dies, they come back to life fully human again. Lea decided to fully join the good guys and got his own Keyblade.

Terra, Ventus, and Aqua were three Keyblade wielders whose adventure took place in the prequel game Birth by Sleep, 10 years before the first Kingdom Hearts took place. Unfortunately, all three of these characters suffered horrible fates. Terra's body was taken over by Xehanort, who needed to replace his own aging body. Ventus's heart was damaged, and needing a place to heal found refuge inside a young Sora’s heart where it rests to this day. His body was also hidden safely away by Aqua, in a place known as Castle Oblivion. Aqua was then trapped in the Realm of Darkness after battling the new and improved young Xehanort. A big piece of Kingdom Hearts 3 will be the quest to save these three. However, that leaves us at eight Keyblade wielders. This is just my speculation, but I believe Terra will be the one left out since Xehanort would have to be defeated before there's any hope of getting him back.

Xehanort

Xehanort is the villain of the series, appearing in almost every entry of the series in various way. He has a long confusing history, so buckle up.

During Birth by Sleep, Xehanort was an old Keyblade master who had become obsessed with Kingdom Hearts, "the heart of all worlds" and a source of great power that has never really been seen or explained. He believed equal parts light and dark coming together would cause Kingdom Hearts to appear. He was wrong, and his attempt is was fractured Ventus' heart. However, his attempt to take over Terra's body and become young again was unfortunately successful.

He then fell into a group of scientists, led by a man named Ansem. He behaved himself for a while, but eventually began experimenting with darkness. He persuades the other scientists to his side, and together they threw Ansem out of the group. Ansem was a famous guy, so Xehanort stole his name and started doing darkness research in it.

Eventually, he went to far. He and the other scientists were split in two. One half became monsters called "Heartless", the other retained human form but without hearts. These "Nobodies" as they're called, along with several others who went through the same process formed Organization XIII. It is also worth noting that the Heartless created from Xehanort also retained it's human form, the only Heartless ever to do so.

At some point before this, Xehanort realized the flaw in his original plan to create Kingdom Hearts. He originally thought equal parts light and darkness would create it, but he now realized that what was actually necessary was seven parts light to thirteen parts darkness. He created the Organization hoping to eventually implant each of them with a piece of his own heart, creating thirteen equal darknesses. However, it turned out the only two members suitable for the task at that time were Siax and Xigbar. Before Xehanort was able to take his plan any further his Heartless, his Nobody, and the rest of Organization XIII were all defeated by Sora in Kingdom Hearts 1 and 2.

True Organization XIII

As stated earlier, when someone who has become a Nobody dies they come back to life fully human. Xehanort was no different. Not only that, but he came back with a new plan to create Kingdom Hearts. He would create a new Organization XIII, but this time he wasn't going to leave anything to chance. Instead of only relying on others hopefully being capable of having a piece of his heart implanted in them, several members of this new organization were previous versions of himself brought to the present through time travel. This new Organization will be the villains in Kingdom Hearts 3, and so far eleven of them have been revealed.

First, the four versions of Xehanort at various points in his life. There's Young Xehanort, hailing from a time period many years prior to any seen before; Heartless and Nobody Xehanort, or Ansem and Xemnas as they called themselves at the time; and Old Xehanort from the time period of Birth by Sleep. Current day Xehanort has yet to be shown, but I have to imagine he'll be there.

The next two members are the former members of the old Organization XIII who already went through the implantation process, and were also brought back fully human after their Nobodies' deaths. Braig(formerly called Xigbar when he was a Nobody) and Isa(formerly Siax) are seen in earlier events with normally colored eyes, but once they are implanted their eyes become yellow. These yellow eyes are the sign that they are now partly Xehanort.

Then there's three more members of the old organization: Larxene (real name unknown), Luxord (real name unknown), and Lauriam(formerly Marluxia). These three have not been seen since their Nobodies died outside of KH3 trailers, but their yellow eyes in those trailers give away that they have been implanted. Marluxia is seen with both regular and golden eyes in two different trailers though, so maybe this doesn't happen until partway through the game.

Next is Vanitas. Remember how Xehanort tried to bring together equal parts light and dark, resulting in Ventus’ heart being fractured? Well the way he did that was by first separating Ventus into two beings, one of pure light and one of pure darkness. The pure light being maintained Ventus’ identity. The pure dark being, however, was known as Vanitas. He looks like Sora with black hair because anime, although he is usually wearing a distinctive black helmet which covers his face. Vanitas and Ventus rejoined near the end of Birth by Sleep, and fought for control of the body. It’s this struggle that caused the damage to Ventus’ heart, but it seems Vanitas was able to escape. He once again has his own body and, going by his new coat, a place in the new organization.

Lastly is Aqua. As I mentioned earlier she was trapped in the Realm of Darkness, and she's been there now for at least 12 years. Last we saw of her in a scene set shortly after KH2 she seemed to still be hanging on, but going by the stinger at the end of the Frozen trailer that might not be the case any more. She has golden eyes and white hair, so she's clearly been implanted. I'm hoping she doesn't actually become a villain, hopefully Riku and Mickey can save her before she fully joins or it's just some sort of fake out.

The last few members of the new Organization XIII are yet to be revealed. In Dream Drop Distance twelve of the thirteen members had already been gathered but aside from the four versions of Xehanort, Braig,and Isa all of their faces were hidden by hoods. During the course of Dream Drop Distance Xehanort hoped to implant a piece of his heart in Sora to make him the thirteenth member but failed. It is because of this ordeal that all Sora's abilities were lost.

Maleficent and Pete

Maleficent and Pete are the secondary villains of the series. In Kingdom Hearts Maleficent was portrayed as the main villain before a very Final Fantasy like twist revealed that it was actually Xehanort. Since then, she’s teamed up with Pete to gain power in any way she can. Maleficent was most recently seen in the secret ending of Kingdom Hearts Chi. There she is seen viewing the events of the original Keyblade War, which took place thousands of years ago, through an unknown method. As for her motivations going forward, in the Kingdom Hearts 3 Orchestra trailer she is seen asking Hades about the location of a black box. To explain what it is she’s looking for, I’m going to have to explain a bit more about the Kingdom Hearts movie: Chi Back Cover.

While the smart phone game Kingdom Hearts Chi focused on a Keyblade wielder in the time leading up to the first Keyblade War, the movie focuses on the same period but from the perspective of the leaders of the Keyblade wielders. It is there we learn about the Master of Masters and his six apprentices. Having knowledge that he will soon disappear from the world, the Master of Masters gives each of his apprentices a task. To five of them he gives roles to hopefully prevent the upcoming Keyblade war which he has foreseen in a vision. But to the sixth apprentice, Luxu, he gives a large black box which he is never to open and a Keyblade with an ornamental eye. Master of Masters tells Luxu to disappear and view events from afar. This will both keep the box safe and allow Master of Master’s visions of the future to occur, as they come from what the Keyblade’s eye sees. It it also worth noting that many many years in the future this Keyblade eventually comes into Xehanort’s possession, and is the main Keyblade he uses.

From this information, it can be surmised that the black box Maleficent is searching for is the same one given to Luxu those many years ago. She probably discovered it’s existence from watching the events of the Keyblade War, and likely it’s contents as well. But while she might know what’s in it, the audience so far isn’t as lucky. There’s plenty of theories, but none with any hard evidence to back them up.

The Other Hearts Connected to Sora

Another persistent plot element of the series that is sure to come up in Kingdom Hearts 3 is the many beings connected to Sora who are trapped without a body either in Sora’s heart or someone else’s. We’ve already discussed why Ventus is there but there are quite a few more, all of whom Sora hopes to free and provide their own beings. There are three, and all three spring from the incident in the original Kingdom Hearts where Sora himself was split into a Heartless and Nobody.

Throughout the game Kairi had been in a catatonic state, as she had lost her heart. It turned out to have taken refuge inside Sora and the only way to release it was for him to be split. After doing so, his Heartless did something no other had ever done. Because of his strength of heart the Heartless was able to regrow a body and return Sora to a normal human. However, that process left a few things behind.

The first to show up was Roxas, Sora’s Nobody. Normally a Nobody would retain the body and personality of the original, but due to Ventus having taking up residence in Sora’s heart something else happening. The Nobody ended up with the appearance of Ventus and a personality all his own. He was also able to wield the Keyblade. He was taken in by the original Organization XIII, and became their thirteenth member.

Next was Namine. She was another Sora Nobody due to Kairi’s heart being released from Sora at the same time the transformation took place. She ended up as somewhat of an amalgam of Sora and Kairi, taking on both her own appearance and personality. Because of the strange circumstances behind her creation, she was gifted with memory altering powers. Because the original Organization XIII wished to use her powers, they kept her as their prisoner.

Finally was Xion. The organization decided they needed a backup Keyblade wielder in case something were to happen to Roxas. Using data taken from a fight Xemnas has with Sora, they created a clone of him. She was sent on organization missions, but was never considered a true member of the organization. Even the name given to her was a slight in this respect. Anagramed and minus the X it was no i, the imaginary number.

While in Organization XIII Roxas made a deep friendship with Xion and Axel. Meanwhile, during the events of Kingdom Hearts: Chain of Memories, Namine was being kept in Castle Oblivion while several of the members searched it for Ventus’ body. It was during this time that Sora came to the castle. Namine was forced to manipulate Sora’s memory, erasing most of his memories and changing the memories of Kairi into memories of Namine. The Organization planned to use this connection to manipulate Sora. However, Sora defeated all the organization members at the Castle and freed Namine.

Namine needed to return Sora’s memories back to normal, but to do that she needed to erase his memories of the time spent in Castle Oblivion. The process would take about six months, during which Sora slept. Eventually the real Ansem (remember him? More on him in the next section.) and Riku took control of his sleeping body. They realized that in order for his memories to be fully restored, every piece of him had to be added back. That meant Roxas and Xion needed to cease to exist in order for Sora to be saved. Xion went immediately, but Roxas had to be eased into the transition. He was placed in a virtual recreation of Twilight Town, where he lived a normal life until he accepted his fate. Sora then came back, only now with two new residents in his heart. By the end of Kingdom Hearts 2 Namine also rejoined with Kairi, seemingly willingly. It’s also worth noting that Axel’s relationship with Roxas and Xion played a large part in his change of heart later on, seeing as they’re now a part of Sora.

In the Orchestra trailer, Xemnas is seen taunting Sora. He tells him that Roxas is a being that shouldn’t exist, so he will have to use the darkness to bring him back. However, in the Frozen trailer Ienzo (formerly Zexion) tells Sora that they might be able to use the data of Roxas from the virtual Twilight Town to bring him back. We'll see how far Sora is willing to go to save his friends.

Eraqus, Riku Replica, and Ansem the Wise

Very few characters have really “died” in the Kingdom Hearts series. These three seemingly have, but plot threads have come up calling that into question.

First is Eraqus. He was the master of Terra, Ventus, and Aqua from Birth by Sleep. Near the end of the game he finds out about how Ventus was split into two opposite being. He flies into a rage and attempts to kill him, calling him an abomination. At this point, Terra is forced to kill him. But later, after Xehanort has taken over Terra’s body, a conversation takes place internally between them. In it, Xehanort implies that Eraqus’ consciousness hitched a ride on Terra’s heart and still exists in some form. In the E3 2015 trailer, we see a young Eraqus and Xehanort discussing the ancient Keyblade War over a game of weird fantasy chess. So even aside from him possibly coming back to life he will at the very least be in the game in flashbacks.

Next is Riku Replica. This is a character that most would say never had a chance in hell of coming back. Showing up only in Chain of Memories, he was a clone of Riku created by the Organization members at Castle Oblivion to test Riku and Sora’s strength. He is eventually defeated by Riku and seemingly dies. However, in the Theme Song trailer Riku is seen leaving his Keyblade in the Realm of Darkness, proclaiming he can’t use it anymore but the “other me” can. He then seemingly appears shortly in the Pirates of the Caribbean trailer.

Finally is Ansem the Wise. After being overthrown by his colleagues, Ansem becomes a wanderer until meeting Riku in Castle Oblivion. Together they fix Sora, and continue to put a damper on the Organization’s activities. The Organizations plan in Kingdom Hearts 2 is to create a artificial Kingdom Hearts using the hearts set free whenever a Heartless is defeated by a Keyblade. Near the end of the game, Ansem plans to use a machine to destroy this nearly completed fake. The machine overloads and he is apparently killed by the explosion. However his sacrifice weakens the Organization’s Kingdom Hearts to the point that Sora and the gang are able to stop it. Even though thought dead, he is later seen in the Realm of Darkness speaking with Aqua in the Birth by Sleep secret ending.

E3 2018 Update

Just gonna add one thing here due to information that came to light at E3. I'll be editing a bit of the original post too.

In the E3 2018 Pirates of the Caribbean trailer, Larxene calls Elsa "one of the seven pure lights we need, the new seven hearts". In Kingdom Hearts 1, Ansem's(Xehanort's heartless's) plan to obtain Kingdom Hearts involved opening a door to it. In order to do this he needed to collect the seven princesses of heart to use as a key. These were seven woman, the only people in all the worlds who had hearts of pure light. In the original game they were Snow White, Jasmine, Alice, Cinderella, Belle, Aurora, and Kairi. The Organization did say that they would go after the princesses as their seven lights if Sora and co didn't collect seven warriors, but I have no idea how there could possibly be seven new ones since the whole point was that there's only seven. I guess we'll find out.

Conclusion

So that’s it. All the information necessary to understand Kingdom Hearts 3. I didn't say it would be pretty or well written but there it is. After doing all this writing (8 pages in google docs!) I’ve come to the conclusion that maybe there is a bit of nonsense in Kingdom Hearts, but it’s all the better for it.

Edit: Thanks to @rodin and @jacksukeru for suggested additions.