Time Travel
A decent attempt at explaining it.
This can be complicated.
Time travel in Kingdom Hearts can be a bit confusing. There are specific rules that I will try to explain here but not everything is cut and dry.
I will specify there is some speculation here as things are not spelled out specifically. This is gathered through reading, playing games and watching many videos on it. It appears there must be 3 distinct things present to time travel in all cases. I have the following in parenthesis to illustrate my point later.
- (Body) - They must leave their body behind
- (Memories) - There must be someone in that time period who remembers them.
- (Medium) - There must be a medium, which can be a simple object of importance to that individual, or some other method of transfer. It can be ones past or future self.
In Dream Drop Distance, Young Xehanort explains the rules behind his method if time travel These are not universal rules but these applied to him.
- A time traveler must leave their body behind. (Body)
- A version of themselves must be present at the point in time they travel too. (Memories) (Medium)
- After arriving, the traveler proceeds with time normally.
- The traveler cannot rewrite destined events (with some caveats)
- When returning to the point in time you left your memories of your time travelling will be lost.
Ansem, Seeker of Darkness uses his existence as a heart without a body (Body) to reach his younger self (Memories and Medium) and set the plan in motion. Young Xehanort then gathers incarnations from different points in history. When he returns to his own era, his conscious memories of the journey disappear, but the experiences remain impressed on his heart and guide his future choices.
KHIII gives visiting hearts replica vessels (Medium) so that they can remain physically present alongside the restored Master Xehanort. Defeating those vessels sends the displaced hearts back to their original times. This is why defeating Young Xehanort does not erase the older Xehanort or undo the earlier games.
Union χ introduces the lifeboats. Their incomplete construction allows a passenger's body to be stripped away (Body) while the heart travels into the future. A medium connected to the person and someone who remembers them can allow the body to be reconstructed at the destination. Maleficent uses this route to return to her era, while other departures carry ancient wielders such as Ventus into later history.
In KHIII, Sora's reversal of the guardians' defeat in KHIII is an exceptional abuse of the power of waking, with consequences of its own constitutes Time Travel. His subsequent repeat of this to save Kairi breaks the rule of not changing history thus erasing him from existence.
This brings up the point of changing history, its unclear if all these time travel events were supposed to happen or were specified by the Book of Prophecies as supposed to happen therefore not "Changing History". It could be argued that the more someone abuses the Power of Waking to change fate, reality itself will correct by removing you from it, making you dissapear. This is all speculation and its unclear how this all actually works.
There are some instances of potential Time Travel that could break these rules, but it should be noted that these were introduced before the Lore of Time Travel. KHII's doors to Timeless River are another special case: characters travel bodily into Disney Castle's past.
This all helps explain how ancient people can reach later eras such as Ventus, Elrena, Brain, Laurium and possibly Skuld showing up in the future eras.
Related
Tagged in
- The Power of Waking (Story & Lore)
- Young Xehanort (Characters)
Sources
Established rules and story events are distinguished from unresolved questions about KHIV.