I know this has been touched before but...

[Launchpad]

"You shall be judged, hahaha yeah!" hop "Aaaaaah!!!!" SPLAT "oh no i'm dead for good, my heart has stopped beating and there's absolutely no chance of me coming back!!!"

Many characters have died in Kingdom Hearts. They just don't typically kill off original characters, because Nomura likes to bring dead guys back.

 

[The Toketsukage]

The Ansem Reports state that the soul, not the heart, dictates life and death. Whenever a heart leaves a body, the body does not die. Many of the characters have been in dubious points of existence throughout the series, but very few have actually died.

That's true, but what I mean is that the heart is what defines who a person is, the heart is them. It is the source of identity. The soul on the other hand seems to just be like a fuel for the body to live. So yes when the soul leaves the body, when the fuel runs out, the body dies. But what would remain after the death of the physical body? The heart. So where does the heart go? It's been implied and hinted in the series that it goes back to Kingdom Hearts. Now if we take the idea that has been stated in the series multiple time to heart "Kingdom Hearts is where all hearts are born and all hearts return to" then it may be that this is suggesting that there is a cycle of reincarnation when it comes to the heart.

Although there is the fact that when visiting the underworld in KH2 we do see many floating misty orbs which may in fact be souls since this is a common depiction in japanese material of souls. So that does kind of makes one wonder exactly what is the soul in the KH series. The soul isn't really talked about except in the Ansem and Secret Ansem Reports.

 

[The_Echo]

Which is why I think they'll leave it vague. I don't know if Nomura's interested in creating rules for life and death and afterlifes and souls. Because when series start being dealing with "the afterlife" they never really escape. I think them bringing the characters back to a physical state is good/close enough.

The Report seems to imply, to me at least, that death in a finality.

Or at the very least, much like in real life, there is no clear answer to what lies beyond death's door, but it's accepted as a definitive end.

 

[Face My Fears]

Ursula was killed in KH1, and came back to life in KH2.

 

[Solo]

Ursula was killed in KH1, and came back to life in KH2.

One can say that she might have been brought back by some dark powers in play (which if I remember correctly is precisely how the Journal put it), but the fact Ariel didn't remember her was just really hard to brush off and it seems like a gaping maw of a discontinuity to me. It was as if everything in KH2 Atlantica took place entirely outside the canon.

 

[Gram]

Ursula was killed in KH1, and came back to life in KH2.

Clayton also died, though he never came back. Oogie Boogie died and Maleficent brought him back though. None of the other disney villains have actually died.

And about death being vague, well it's best to remember that Nomura said that "there is no death in kh" and to an extent this is true. Yes we know that the body does indeed die when the soul fades away, this if what you could consider "natural death" but as pointed out already the heart always remains so in a sense you never truly die.

What may determine if a death is permanent or not would likely depend on where the heart goes once it's body has died. It is this aspect that has never been elaborated on and I think Nomura likes it that way.

 

[kuraudoVII]

Death has been handled in an odd way in this series. Going by what we've seen, most people that have died were either not necessarily dead or have been brought back by various means. This is particularly noticeable with Maleficent who was brought back by Flora, Fauna, and Merryweather remembering her and Auron who was brought back by Hades, the Lord of the Dead. Very few characters seemed to have actually stayed dead, so who knows how permanent death is in this series. It's almost as if Tetsuya Nomura took a page out of Akira Toriyama's book and decided that death is just a slap on the wrist.

 

[Sephiroth0812]

Clayton also died, though he never came back. Oogie Boogie died and Maleficent brought him back though. None of the other disney villains have actually died.

And about death being vague, well it's best to remember that Nomura said that "there is no death in kh" and to an extent this is true. Yes we know that the body does indeed die when the soul fades away, this if what you could consider "natural death" but as pointed out already the heart always remains so in a sense you never truly die.

What may determine if a death is permanent or not would likely depend on where the heart goes once it's body has died. It is this aspect that has never been elaborated on and I think Nomura likes it that way.

That is however only because no one decided to actually revive him and Deep Jungle was never used again. If Maleficent could revive Oogie Boogie, she surely could do so with Clayton if she wanted to.
"Death" in the KH verse seems to be nothing but a deep, normally eternal sleep, but some powerful beings and/or procedure can awaken someone from such a sleep.
Maleficent's "resurrection" by the three fairies remembering her has actually been foreshadowed in Chain of Memories as Ansem explains the whole procedure word for word:

Ansem: That's it, remember me... Let me drift into your heart...

Riku: Ansem!

(Ansem laughs)

Ansem: You called out my name. You have been thinking about me... You're afraid
of the darkness I command. Good... The more you think of me, the closer my
return draws. And when I have awoken, I will take hold...

Riku remembering and thinking about Ansem eventually would have enabled his return/reawakening, essentially a "Birth by Sleep" in the truest sense of the words. The same happened with Maleficent in KH 2 as Flora's outburst shows:

Flora: No! We mustn't remember her name! Oh dear...

Since the heart is like your essence/spirit, I guess that "death" would then be truly permanent if no one really remembers you anymore and there is no more connection to any other hearts that are still "alive" in the physical sense.
Otherwise, the possibility of returning would always be there, although it doesn't mean it has to happen in every case.

 

[Launchpad]

That is however only because no one decided to actually revive him and Deep Jungle was never used again. If Maleficent could revive Oogie Boogie, she surely could do so with Clayton if she wanted to.

Sabor the leopard is never coming back.

The moment Sabor died was the moment Sora became a hard-boiled mofo.

 

[Gram]

That is however only because no one decided to actually revive him and Deep Jungle was never used again. If Maleficent could revive Oogie Boogie, she surely could do so with Clayton if she wanted to.
"Death" in the KH verse seems to be nothing but a deep, normally eternal sleep, but some powerful beings and/or procedure can awaken someone from such a sleep.
Maleficent's "resurrection" by the three fairies remembering her has actually been foreshadowed in Chain of Memories as Ansem explains the whole procedure word for word:

I know this, I never said otherwise.
Ansem is a bit of different case dont you think? Maleficent backs your point but Ansem wasn't truly dead, he (or a part of him, either way) remained in riku after his defeat in kh1.

Riku remembering and thinking about Ansem eventually would have enabled his return/reawakening, essentially a "Birth by Sleep" in the truest sense of the words. The same happened with Maleficent in KH 2 as Flora's outburst shows:

Again Ansem is different to Maleficents case. Maleficent backs your claim more than Ansem.

Not saying your wrong mind you just that Ansem's situation wasn't the same as Maleficent, a part of him was there to return whereas Maleficent only had her cloak and raven left behind.

Since the heart is like your essence/spirit, I guess that "death" would then be truly permanent if no one really remembers you anymore and there is no more connection to any other hearts that are still "alive" in the physical sense.
Otherwise, the possibility of returning would always be there, although it doesn't mean it has to happen in every case.

It's clearly not that simple as if it was everyone that had "died" would return simply because they were remembered by their loved ones (or enemies).
And we both know a memory doesn't die with the person the memory is based on since Sora clearly remembered Maleficent as did Pete. (though them remembering didn't bring her back)

Your part on sleep is the key factor, Maleficent once said she has "power of sleep" and as we know even if the body croaks the heart is always left behind.
What may determine resurrection may more rely on waking the heart that has fallen into slumber, thus also adding substance to the line "birth by sleep".

 

[Sephiroth0812]

Sabor the leopard is never coming back.

The moment Sabor died was the moment Sora became a hard-boiled mofo.

While that may hold true (as any other element involving Deep Jungle), the possibility would still be there even for that Leopard. ;P

I know this, I never said otherwise.
Ansem is a bit of different case dont you think? Maleficent backs your point but Ansem wasn't truly dead, he (or a part of him, either way) remained in riku after his defeat in kh1.


Again Ansem is different to Maleficents case. Maleficent backs your claim more than Ansem.

Not saying your wrong mind you just that Ansem's situation wasn't the same as Maleficent, a part of him was there to return whereas Maleficent only had her cloak and raven left behind.

There may be variances in their dispositions, but the basic situation is the same. For all intents and purposes, both Ansem and Maleficent where existing no more on the physical layer of reality. According to Vexen, Maleficent was in the Realm of Darkness while Ansem was inside Riku's heart, that's merely a difference in location.
Maleficent wasn't "truly" dead either if we go by Vexen's explanation, as he only said that she's "gone" and cannot return of her own volition, but never actually ruled out a return in itself.

All in all, I was also pointing out more the process itself rather than looking in detail on Maleficent's or Ansem's individual cases.

Like I said above, there are some variances/differences between them, but the core process as to how they came eventually back is the same.

It's clearly not that simple as if it was everyone that had "died" would return simply because they were remembered by their loved ones (or enemies).
And we both know a memory doesn't die with the person the memory is based on since Sora clearly remembered Maleficent as did Pete. (though them remembering didn't bring her back)

Your part on sleep is the key factor, Maleficent once said she has "power of sleep" and as we know even if the body croaks the heart is always left behind.
What may determine resurrection may more rely on waking the heart that has fallen into slumber, thus also adding substance to the line "birth by sleep".

You're completely correct on that one, it is obvious that we are still missing one or more pieces of the whole process, namely exactly the piece(s) that prevent this process from happening naturally and every time.
It is an oversimplication, yes, but a starting point from which we can go further.

Sleep is indeed another key factor, as we can see in DDD when looking at the sleeping worlds (worlds have hearts too and therefore work exactly like persons). Some (the majority actually) of the worlds restored at the end of KH 1 had their "Birth by Sleep" and were restored, but several of them didn't and they remained in sleep, eternal sleep even until Sora (Riku actually didn't do anything because he was in Sora's dreams) manually opened the Keyholes of Sleep.
Sora himself also awoke only after 1. Riku defeated the Nightmare trapping his heart, 2. opened a Keyhole on Sora's heart station (most likely Sora's personal "Keyhole of Sleep") and 3. answered the questions of Roxas, Ven and Xion which was, in Ansem the Wise's words "the last key" to freeing (and awakening) Sora.

Ansem the Wise: He's not here. You see, by defeating the Nightmare
imprisoning Sora, you freed him.

Riku: You mean...the Sora wrapped in that black phantom?

Ansem the Wise: Then, you came here, and you were questioned by three
young people. That was the final key to awaken him. Sora is awake. You
can go home now.

So, as I theorized before DDD came out and as you point out in the last sentence, there are several conditions to fulfill in order to truly "revive" someone, explicitly waking the sleeping heart itself being another one of them, not to mention we may not know every condition yet.
Not to mention that for existences who consists only of a heart, like Naminé, Xion, Roxas (and possibly Eraqus) right now, the process might be even more complicated.

This explains also why it doesn't happen all the time or in general more often. We only saw/see it so often because there are several characters among the wider central cast (among them Maleficent, Xehanort, Riku and possibly Sora) who may possess all the needed abilities in order to fulfill all those conditions.
It is certainly not as easy (and cheap as some may say) like in Dragon Ball or Sailor Moon to bring someone back.

 

[Gram]

Indeed, one of the bigger mysteries of the process (like in the aforementioned Roxas/Namine/Xion) case is physical form. Unlike Sora or the sleeping worlds they no longer have a physical shell that they can just wake up into and walk off. (So to speak)

We already know Sora and Riku can wake hearts now, Riku demonstrated it, however they still lack means of which to restore physical form. (which is likely how the data Diz left in rikus hands will contribute)

And I'm hoping the data can only restore Roxas, Namine and Xion so it doesnt end up becoming like the already pointed out Dragonball.

Also looking back it would seem sleep serves as the series afterlife since it is into darkness/sleep they go to when they lose presence/"die".

 

[Guernsey]

Here is an excerpt from the wikipedia page that describes the Xehanort method of time travel. It essentially means that time is immutable in the Kingdom hearts universe and it could lead to some paradoxes. Keep in mind, it isn't the only method that i describe in the article but it is the method that I saw in the game.

Here are some more time travel plot devices in fiction.

1. There is a single fixed history, which is self-consistent and unchangeable. In this version, everything happens on a single timeline which does not contradict itself and cannot interact with anything potentially existing outside of it.

1.1 This can be simply achieved by applying the Novikov self-consistency principle, named after Dr. Igor Dmitrievich Novikov, Professor of Astrophysics at Copenhagen University. The principle states that the timeline is totally fixed, and any actions taken by a time traveler were part of history all along, so it is impossible for the time traveler to "change" history in any way. The time traveler's actions may be the cause of events in their own past though, which leads to the potential for circular causation and the predestination paradox; for examples of circular causation, see Robert A. Heinlein's story "By His Bootstraps". In fiction, these phenomena are often referred to as "stable time loops".[citation needed] The Novikov self-consistency principle proposes that the local laws of physics in a region of spacetime containing time travelers cannot be any different from the local laws of physics in any other region of spacetime.[80]

1.2 Alternatively, new physical laws take effect regarding time travel that thwarts attempts to change the past (contradicting the assumption mentioned in 1.1 above that the laws that apply to time travelers are the same ones that apply to everyone else). These new physical laws can be as unsubtle as to reject time travelers who travel to the past to change it by pulling them back to the point from when they came as Michael Moorcock's The Dancers at the End of Time or where the traveler is rendered a noncorporeal phantom unable to physically interact with the past such as in some Pre-Crisis Superman stories and Michael Garrett's "Brief Encounter" in Twilight Zone Magazine May 1981.

 

[Gram]

The point isn't that paradoxes can't be made but rather that history can't be altered.
In fact, depending on how you view it, we've seen a couple paradoxes already.

Like for example in kh2 when Maleficent tried to change history, her actions caused thorns and heartless to appear in the Disney Castle which it's cornerstone is supposed to prevent.
Or you could even take Xehanorts use of time travel as a paradox since he's literally pulling bits of the past, himself, to the present with all of them existing simultaneously at one time.

Hell even the stop magic used in the series is a form of warping time as it stops the opponent you cast it on in their tracks by essentially halting their perception/space-time around them.

However, as pointed out in that link, none of them are long lasting as time will resolve them come hell or high water.
(which is something Xehanort admits too when he points out a couple times during his speech that 'events destined to happen cannot be changed')