Based off of interviews, replaying the game multiple times, and various forums, this is how I’ve come to understand KH3D and its many tricky plot elements. If there is anything I don’t cover, PLEASE COMMENT! I am, after all, trying to learn & understand just like everyone else.
Time Travel
Various books, films, and television shows have presented many forms of how time works, and I think that is where some KH fans first get confused. The timeline in the KH universe is not just a straight line (with an already established future), nor is it a line with multiple lines springing from it (alternate timelines or dimensions). Think of time in KH as a line that is continuously moving forward (with an unwritten future). You can perform actions in the present and shape your own future, but the actions of the past are cemented in time and cannot be altered. This is why no one (good or bad) from the future can go back to change the present, nor someone from the past to base their decisions on future events. These rules are forced upon everyone, but there are two KNOWN methods of time travel:
The Magic Method: Someone with powerful magic (Yen Sid, Merlin, and even the Three Good Fairies to an extent) can simply open a portal and have people walk through to the past, with no repercussions or time limits.
The Xehanort Method: By discarding your body and becoming a heart, you are free to roam the timeline wherever a version of you is present, but must return to the time & place of when you initially departed for your time adventure after an undetermined amount of time. Anyone you pick up along the way doesn’t have to lose their body, but must also return to their point in time and play their part in the timeline.
The Realm of Sleep
When a world in the Realm of Light falls to darkness, it falls into a state of sleep (a.k.a. the Realm of Sleep). From there, it eventually ends up in the Realm of Darkness (as can be seen in the Birth by Sleep Volume 2 trailer). After the events of KH1, all the worlds in the Realm of Darkness returned to the Realm of Light. However, the ones that were still asleep at the time remained in the Realm of Sleep. The RoS is outside of time, and thus why it was possible for Sora & Riku to enter it from the past, but then pop out of it into their current present. It should also be noted that Nomura has said that there may be more sleeping worlds in the Realm of Sleep that we do not know of. I always imagined Dumbo’s world was returned to the Realm of Light, but I guess his world could be in the Realm of Sleep.
The Mark of Mastery
Since Sora & Riku needed a quick crash course to prepare them for Master Xehanort, and the Sleeping Worlds needed to be awakened anyway, Yen Sid sends the duo to the Realm of Sleep to do just that. If they can return after unlocking the Seven Keyholes of Sleep, then they would be dubbed Keyblade Masters. In order to teach them the proper way of Keyblade wielding, Yen Sid makes them physically younger to before they received the Keyblade. Based off the flashbacks, it’s obvious that Yen Sid gave the duo a lot of information before sending them off. He probably told them the proper way of Keyblade combat was using the Deck Commands, thus why he is not there with them in person to instruct. Nomura has also stated that it was Yen Sid that gave them the new clothes. It was Xehanort that gave Sora the X on his shirt (to track him) and Riku received the Dream Eater mark after becoming one. Since Sora “lost focus” during the exam, and Riku conquered a deeper level of sleep, that is why he was the only one to become a Master, even though Sora was the one who actually woke the worlds up.
Xehanort’s Time Travel Plan
After Apprentice Xehanort split into two (Xemnas & Ansem SoD), his Heartless gains the ability to time travel (since he is just a heart), but does not use it immediately. It instead follows Kairi to Destiny Islands and waits. When Sora & Riku arrive from the future, he follows them into the Realm of Sleep. It is from there that the Heartless goes into the past to Young Xehanort and transfers his Time Traveling powers to his younger self, as well as informing him of the plan to form the X-Blade. Having lost his time traveling ability, Xehanort’s Heartless returns to the point before he enters the realm of sleep (since you cannot return to a place that is outside of time). Just as Destiny Islands is disappearing, Xehanort’s Heartless begins to follow and slowly posses Riku (as we see in the events of KH1). Meanwhile, Young Xehanort is able to jump to points in time where a version of himself is present, and begins to collect hearts of darkness. He is also able to go to the Realm of Sleep because that is where Xehanort’s Heartless (a version of himself) originally made the time jump. Since Xehanort’s Heartless time jumped before Master Xehanort was reassembled in TWTNW, that is why the Organization did not know that Lea would come to the rescue and foil their plans.
I hope this helps anyone and everyone! I didn’t think of all this overnight, and I am continuously updating it. So, if there are any comments or questions, please help me to improve my understanding!
