As stated in the game it began with his heartless. He was an existence of solely a heart so he could time travel but he could only go one direction and he needed to exist at that time he was traveling to so ultimately he had to get a younger incarnation of himself to time travel forward even though he didn't even get rid of his body... now, does this really make sense? Lets be honest, no it doesn't. Its nearly worse than math formulas that have to be memorized. Anybody might say "Its a time travel story, do they ever make sense?" but being the stubborn fan that I am, I had to defend the plot. Fortunately even math formulas some times make sense, and this formula is no exception.
Back when I first heard of "the mysterious figures" affiliation to time, I freaked out. "The series is struggling with convolution already how will it handle time travel!" Eventually I came up with a satisfying yet incorrect theory as how he may time travel with the power of dreams. The theory was that if we can traverse entering reality and dreams and if we can traverse time in the dreams, then we can ultimately traverse time in reality. And of course I expanded on to kingdom hearts and the seven sleeping worlds, but that is beyond the point. As it turns out, I was in the ball park. Although not as explicitly stated as the giving up your body part and traveling in only one direction, Ansem SoD and YMX definitely traveled through time via dreams. In this context I think these "rules" just may be starting to make sense.
Why don't we start off with the big picture and then move down to why each rule makes sense.
Just as Sora and Riku allegedly time traveled according to Xigbar and Goofy (and not disagreed to by Yen Sid) Ansem SoD traveled back in time to when his original self was still just a boy. Sora and Riku both had bodies unlike the robed Ansem, but Xigbar refers to both incidents as time travel. Sora and Riku were also reliving the experiences in contrast to Ansem SoD who simply witnessed and interfered with that past. It makes sense to immediately write off Sora and Riku's experiences with destiny islands as time travel, but there's no way the writers could repeatedly make such a mistake and then have Nomura not catch it. Instead might we simply qualify it a less complete type of time travel. So maybe Xehanort's Heartless did time travel in the same way that Sora and Riku did, but by being solely a wandering heart he was able to more literally go back to a specific time.
Lets continue on this aside to develop and understand this "what if." That would mean that Xehanort dreamed himself into the past. He could dream up that time because he already existed there! Assuming that dreams were the mode of time travel, it would appear that we didn't even need to be told that you must have a version of yourself waiting at the destination.
"But wait a second, in that case he didn't even time travel. And YMX definitely wasn't a dream the whole time because he was in the real world that never was."
I guess that's one of the main points I have been sort of tiptoeing around, but you caught me, I don't believe he time traveled in the same sense that we have been assuming he has been. Let me explain a bit further.
In reality it is a combination of both traversing time in dreams and dreams in time. The young Xehanort that we encounter in 3D for most of the time is a figment of Xehanort's memory. So it makes sense that the actual YMX wouldn't have any memory of it, because it never really happened! Two rules down, and uhh... some more to go! However, because his heart and the dream of his heart weren't entirely independent, an impression was left when the dream of his heart allegedly returned to his own time. Ultimately, these two timelines resonated with each other to some arbitrary extent creating a dual reality. What made this impression even more powerful was the fact that YMX was did transcend the realm of dreams to enter reality. When this happened the timer clicked on and YMX and the others could only exist due to powerful time magic coupled with that world's odd existence. After that magic is all used up, its only natural that one must return to his own time. Check rule number three. Put it together as you will, but it makes sense that this is how it worked out.
Take a look at the graphic below. It summarizes up most of this last part not quite to the events of KH3D. (and sorry in advance for the bad grammar, random periods in sentences, and sucky arrows)
If I'm not mistaken we still have two rules left: Upon arriving at destination one can only move forward, and one must discard the body in order to time travel. The first rule here is quite natural and intuitive in any sense so I don't think any further discussion is necessary. As for discarding the body, lets go back to where this discussion began when I pointed out XH's time travel in contrast to Sora and Riku's. A number of distinctions have already been pointed out concerning time in the realm of nothing. There it loses nearly all meaning. This is where the body exists after abandoning the body so when with the body it must still be tied to regular flowing time-even in dreams. In addition to this, the bodily form must be dreamed up which allows one to observe from the outside and intervene with this alternate, yet not entirely independent timeline.
And that is how Xehanort "time traveled."
TLDR;
XH did not really time travel just as Sora and Riku did not really time travel.
The young Xehanort Sora and Riku faced in kh3d was actually a figment of XH's memories/dreams.
A distinction could be made between what actually happened in the time and what happened in certain people's dreams at different times.
XH's dream of YMX resonated with the real YMX to influence him. This resonance was in part acheive by his being realized in the real timeline.
In other words a sort of dual reality was achieved in the two timelines/realities overlapping or resonating.
As stated in the game it began with his heartless. He was an existence of solely a heart so he could time travel but he could only go one direction and he needed to exist at that time he was traveling to so ultimately he had to get a younger incarnation of himself to time travel forward even though he didn't even get rid of his body... now, does this really make sense? Lets be honest, no it doesn't. Its nearly worse than math formulas that have to be memorized. Anybody might say "Its a time travel story, do they ever make sense?" but being the stubborn fan that I am, I had to defend the plot. Fortunately even math formulas some times make sense, and this formula is no exception.
Back when I first heard of "the mysterious figures" affiliation to time, I freaked out. "The series is struggling with convolution already how will it handle time travel!" Eventually I came up with a satisfying yet incorrect theory as how he may time travel with the power of dreams. The theory was that if we can traverse entering reality and dreams and if we can traverse time in the dreams, then we can ultimately traverse time in reality. And of course I expanded on to kingdom hearts and the seven sleeping worlds, but that is beyond the point. As it turns out, I was in the ball park. Although not as explicitly stated as the giving up your body part and traveling in only one direction, Ansem SoD and YMX definitely traveled through time via dreams. In this context I think these "rules" just may be starting to make sense.
Why don't we start off with the big picture and then move down to why each rule makes sense.
Just as Sora and Riku allegedly time traveled according to Xigbar and Goofy (and not disagreed to by Yen Sid) Ansem SoD traveled back in time to when his original self was still just a boy. Sora and Riku both had bodies unlike the robed Ansem, but Xigbar refers to both incidents as time travel. Sora and Riku were also reliving the experiences in contrast to Ansem SoD who simply witnessed and interfered with that past. It makes sense to immediately write off Sora and Riku's experiences with destiny islands as time travel, but there's no way the writers could repeatedly make such a mistake and then have Nomura not catch it. Instead might we simply qualify it a less complete type of time travel. So maybe Xehanort's Heartless did time travel in the same way that Sora and Riku did, but by being solely a wandering heart he was able to more literally go back to a specific time.
Lets continue on this aside to develop and understand this "what if." That would mean that Xehanort dreamed himself into the past. He could dream up that time because he already existed there! Assuming that dreams were the mode of time travel, it would appear that we didn't even need to be told that you must have a version of yourself waiting at the destination.
"But wait a second, in that case he didn't even time travel. And YMX definitely wasn't a dream the whole time because he was in the real world that never was."
I guess that's one of the main points I have been sort of tiptoeing around, but you caught me, I don't believe he time traveled in the same sense that we have been assuming he has been. Let me explain a bit further.
In reality it is a combination of both traversing time in dreams and dreams in time. The young Xehanort that we encounter in 3D for most of the time is a figment of Xehanort's memory. So it makes sense that the actual YMX wouldn't have any memory of it, because it never really happened! Two rules down, and uhh... some more to go! However, because his heart and the dream of his heart weren't entirely independent, an impression was left when the dream of his heart allegedly returned to his own time. Ultimately, these two timelines resonated with each other to some arbitrary extent creating a dual reality. What made this impression even more powerful was the fact that YMX was did transcend the realm of dreams to enter reality. When this happened the timer clicked on and YMX and the others could only exist due to powerful time magic coupled with that world's odd existence. After that magic is all used up, its only natural that one must return to his own time. Check rule number three. Put it together as you will, but it makes sense that this is how it worked out.
Take a look at the graphic below. It summarizes up most of this last part not quite to the events of KH3D. (and sorry in advance for the bad grammar, random periods in sentences, and sucky arrows)
If I'm not mistaken we still have two rules left: Upon arriving at destination one can only move forward, and one must discard the body in order to time travel. The first rule here is quite natural and intuitive in any sense so I don't think any further discussion is necessary. As for discarding the body, lets go back to where this discussion began when I pointed out XH's time travel in contrast to Sora and Riku's. A number of distinctions have already been pointed out concerning time in the realm of nothing. There it loses nearly all meaning. This is where the body exists after abandoning the body so when with the body it must still be tied to regular flowing time-even in dreams. In addition to this, the bodily form must be dreamed up which allows one to observe from the outside and intervene with this alternate, yet not entirely independent timeline.
And that is how Xehanort "time traveled."
TLDR;
Edited by keystrike