What happens to its soul?

The dragon is both dead and alive. Only when the Dragonborn collapses the wave function does a dragon lose its soul.

If another Dovah doesn't eat it...I think it gets a time-out until Alduin tags it back in, right?

What if you killed alduin then what happens?

From what I've read, you can't kill Alduin. The best solution has been to push him forward in time and then to banish him from the world for a while. . . he'll be back.

Just because arngeir speculates that alduin didn't die doesn't make it true.

Is there good evidence for the alternative? If Alduin had died, wouldn't it have caused some serious time breaking?

True, but Alduin is a big fragment of an aedra, who are already dead anyways.
Not to mention he's the universe's failsafe to devour the world before the kalpa falls apart. Alduin simply being slain would be too easy to destabilize the Mundus.

Not if Alduin isn't Borhamu.

If a tree falls in a forest and no one is around to hear it, does it make a sound?

We've already seen what happens when a dragon dies and a Dragonborn does not steal its soul. Not only is that what happened to Nafaalilargus, but also to all of the other dragons in Skyrim before the return of Alduin. They lay around before Alduin swoops down and resurrects them.

Arngeir knows what we have known long before Skyrim was even released. Alduin is the Nordic aspect of Akatosh. You cannot kill Alduin, and if you somehow did, it would cause a Dragon Break unlike any Dragon Break we've ever seen in the past.

It would be more of a return to the Dawn I think... that's only if Alduin really is Aka. Plus, the pact would be invalid and Dagon would be all up on our [censored].

Honestly, I'm having a hard time believing this. If dragons can't come back without Alduin, I just can't see people needing a dragonborn to kill dragons throughout the first and second eras since any good warrior can come along and "kill" them all the same.

Given all the new dragon lore Skyrim dumped on us, which I generally like, this is really my biggest peeve with it.

I still say other dragons can revive them as well. Just never did for some reason I completely fail to understand.

Eeven if dragons are dangerous creatures, they were near extinct at the end of the 2nd era: the few still alive were hiding, without Alduin they just stayed dead after all. You don't need a dragonborn to "disable" a dragon but to fight Alduin: the only way to learn the dragonrend shout without spending decades of meditation .

@Fishy: if all you need is a (powerfull) shout then yes, other dragons should be able to revive each others. But given their very nature (they are selfish, arrogant and try to dominate any creature they meet), reviving a dragon looks like reviving an enemy if you can't dominate him. Alduin was the only one strong enough to make them biw before him.

Any good warrior can "kill" dragons, in the way that their soul is preserved and ready for resurrection from Alduin. That's why dragons were so rare. Alduin had been sent forward in time, and the ancient Nords killed the rest of the dragons and made the tombs for them that we see around Skyrim. Without Alduin to resurrect them, they just remained skeletal corpses in the ground. The Dragonborn is just the only thing that can kill them permanently by absorbing their souls.

What happens to the souls of dragons absorbed by a dragon born, when said dragon born dies or is killed?

To answer the OP's question, it would appear dragons just simply die if their souls are not absorbed. I'm guessing the Dragon Cult buried the dragons in such a way that something of their bodies remained intact so that their soul could eventually be reunited with it by Alduin. In other words, dragons die like anything else but can be brought back by Alduin if their soul, and a remnent of their body, is available. This is mostly guess work of course, but I tried basing my speculations on facts imbibed from gameplay as well in-game sources.

See the ending of Oblivion, that's pretty much what would likely happen. After all, when the emperors and empresses performed the lighting of the dragonfire rites, they are binding themselves to the dragon, which makes them have the soul of a dragon.

You mean the sudden appearance of a colossal, avatar of Akatosh?

Hmmm, I was thinking that the dragon souls themselves dispersed and could subsequently be reanimated by Alduin provided he was around.

Though that only matters when Alduin is around. If Alduin's gone he can't resurrect them, so any dragon "killed" by a non-Dragonborn would be just as "dead" as one killed by a Dragonborn.

No one knew Alduin was sent forward in time and would come back, since the Tongues that beat him had no idea what the Elder Scroll would do. It was a very desperate move since they didn't really know what it would do and could've backfired horribly. Even Paarthurnax didn't know for sure what happened and needed to stay to keep an eye on the time wound.

Also, it was over 2500 (two thousand five hundred) years between the defeat of Alduin and the arrival of the Dragonguard, who for some reason still believed they needed a Dragonborn to kill dragons, and it was kept that way for another 1000 years or so until Tiber Septim came along and granted safe harbor to the remaining dragons. So that's nearly 40 (forty) generations of men that somehow knew they still needed a Dragonborn to prevent Alduin from resurrecting dragons, when no one knew Alduin was going to come back. That just doesn't make sense to me.

Alduin and his ability to resurrect dragons should've been the stuff of myth and legend well before the Dragonguard showed up. The idea that he'd come back and resurrect fallen dragons should've been stories parents would tell to scare their children by that time. I have a really hard time believing that after a few generations people would continue to believe in earnest Alduin's power and ability to resurrect dragons, let alone a few dozen generations.

Except the dragon killing continued through the first era (almost 3000 years) as it was still happening when the Dragonguard came, and through the second (almost 1000 years) since the Reman dynasty hunted dragons, until Tiber Septim came along and offered the remaining ones protection. So for almost 4000 years, dragons that were "killed" stayed "dead" regardless of if they were killed by a Dragonborn or not, yet people continued to believe a Dragonborn was needed to kill dragons? That just doesn't add up.

Esbern himself said that anyone can kill a dragon, that's not the problem.

The problem is Alduin himself, only the Dragonborn can deal with him.

I'm under the assumption that the only ones that truly remember how to truly off the Dragon, would be the Blades lore keeper man. So far (And I may be forgetting some pivotal dialog pertaining to this.), I think the most the average Nord believes that the Dragonborn steals their power, but anyone can slay one. Its safe to say that they think only a dragonborn can 'kill a dragon' on the premise of being a good dragonhunter, not the soul stealing.

But what I'm saying is that it wouldn't make sense for people to think Alduin was still any threat, since they didn't know he was going to come back. After 2500 years, the Dragonguard would have no reason to believe it other than some vague oral prophecy they've been passing down for who knows how long, and the Nords/Imperials they were assimilated by would have no reason to believe the prophecy. Also...

The thing is, the term "Dragonborn" was first used when Akatosh gave St. Alessia blood from his heart, forming a covenant to keep Oblivion at bay. What people knew of the Dragonborn wasn't at all related to dragon-killing or Alduin-bashing, it was to protect Tamriel from Oblivion by ruling and keeping the Dragonfires lit. It wasn't until the Dragonguard came, about 2000 years or so later, and said "oh yeah, and the Dragonborn is totally awesome at killing dragons and dealing with Alduin and stuff" that this somehow became part of their legacy, despite the fact that normal people had been "killing" dragons for over 2500 years (nearly 30 generations), and there being no direct threat from Alduin.

The dragons die, but they can still be resurrected by Alduin. Alduin's shout is something like reversing time, so he probably undoes their deaths. But their souls can't be restored to their bodies if Dragonborn absorbs them.