So I read that there was an Emperor who was killed trying to conquer Akavir? My question is how did they recover the Amulet of Kings and return it to Tamriel on time?

Do we know that he had it with him?

Nero,

It is my assumption that the emperor either did not carry the Amulet into battle (leaving it with the garrison) or that it was taken back by the two survivors of the last assault. It is also possible that he did not take it into Akavir, however, I do not find this likely given the amulet's symbolic value.

Ayaan-Si

But wouldn't Oblivion gates start opening throughout Cyrodiil if he wasn't wearing it?

Oblivion gates don't open because the Emperor isn't wearing the amulet, but because of the Dragonfires, notice how even when Martin wore the Amulet of Kings you had to go to the Temple of the one to relight the dragonfire

Not if he left it with his heir.

The lore of Uriel V has been around longer than the rather peculiar idea that if the Dragonfires aren't burning, then Daedra can invade. The best answer I can give to you about why Dagon didn't muster his dremora, is because the Heart of Lorkhan was still in Red Mountain, making the barrier strong enough that the Dragonfires didn't need to be lit.

But that's an excuse, not an answer.

Nero,

The Amulet of Kings does not determine the status of Oblivion gates, and neither does, for that matter, Alessian blood. Notice the hundreds of years when the amulet was not worn, such as most of the 1st and the entirety of the second era. There were no major Oblivion invasions during those times. It is also important to note that smaller invasions (such at the destruction of Mournhold in 1E2920) occurred while the Dragonfires were burning.

In obsolescence,
Ayaan-Si

What happened when there wasn't an empire? As in, before Tiber? (Oblivion gate wise)

The barriers between the Mundus and Oblivion are (or were) protected by more than just the Amulet of Kings; they are (or were) protected by a system of multiple towers and stones. The last two towers standing were Red Mountain, whose stone was the Heart of Lorkhan; and White-Gold Tower, whose stone was the Amulet of Kings. These barriers prevent the creation of a stable http://www.uesp.net/wiki/Oblivion:Liminal_Bridges.

The Red Mountain tower is of still greater antiquity than White-Gold Tower, dating back to the death of Lorkhan. Large-scale Daedric incursions were impossible due to its presence, even before the creation of the Amulet of Kings, and even during the chaos of the Second Era. But when the Nerevarine freed the Heart of Lorkhan, Red Mountain fell. This left only White-Gold Tower, with the Amulet of Kings as its stone, preventing the widespread creation of stable portals to Oblivion. Then the Emperor died, and the Amulet of Kings was stolen, taking down the last tower, and allowing the Mythic Dawn to open the gates for the invasion.

There are others though. They're obsolete, then?

Maybe the others towers do something a little different?

I 'unno. I'm just kinda rolling with it right now.

The two larger towers obviously held most of the daedra at bay.

The smaller ones may have held some back to a degree, but, they either

1) Didn't work because of everything was connected, thus, when the larger towers fell, they ceased to work.

or

2) Worked, but weren't enough to hold back Daedra.


Possibly, towers, according to size, held back daedra from areas.


With the two large sources gone, the smaller ones (possible all connected) were not able to hold back the massive power of Oblivion. As more gates open, daedric power on Nirn spread, and the connection as not as weak. That could have also caused the whole barrier to go down.


Lots of it is theory, but it is obvious, that the barrier was mainly supported by the two large towers.

Obsolete? More than likely destroyed in one of the hundreds of wars throughout the ages.

Even if there are others, they are not major, and cannot support a large barrier.

There are most certainly others. Adamantine to name just one.

Yes, but the white gold tower is obviously a major chunk of the barrier.

Who says, that the mythic dawn did not remove the other stones? It is possible.

The High Elven tower - Crystal-Like-Law, not "major" ... ? Taking into consideration, high elves here, that one really should be second behind Red Mountain.

And there's Snow-Throat of Skyrim

Yeah, but not so much. The Nords are in no hurry to swim in the Aether anytime soon.

Allow me provide a quick summary of the Towers.

Direnni - Balfiera, Highrock, functioning.
Red-Tower - Red Mountain, Morrowind, destroyed in Morrowind.
White-Gold - The White Gold Tower, in Cyrodiil City, destroyed before the Oblivion Crisis, restored by Martin's martyrdom.
Crystal-like-Law - Crystal Tower, Summursets, functioning.
Orichalc - Tower of Yokuda, destroyed during the cataclysm.
Green-Sap - believed to be Falinesti, rooted.
Walk-Brass - Numidium, used by Tiber Septim, destroyed in Daggerfall.
Snow Throat - High Hrothgar of Skyrim, functioning.

The Khajiit's Lunar Latice can also be considered a type of Tower. Given this, it is safe to assume that other similar relationships exist.

The main purpose of the Towers is not to keep the Daedra from attacking Tamriel but as "a focus point for (re-)reaching the divine." They tie into the stability of Tamriel in general, or perhaps rather the lack thereof. They were not built as a barrier from the Daedra, and to assume that they act primarily as such is, at the very least, dangerous.

The Dragonites struck at a very opportune moment, and their ritual involved much more than the murder of an emperor and the theft of an amulet.

Conversely,
Ayaan-si

If you really wanna look at it, Adamantia is the most important tower, because all the other towers (except Red Tower) were made as "copies" of it.

White-Gold Tower is only prominent because it is located in Cyrodiil.

I know a bit of lore, but I am no lore buff.

Well, what else exactly opened up the jaws of oblivion?

Did the actual requirement change over time?

You are saying that the towers do that, but that is not the primary purpose.


As in, as the towers were destroyed over time, the barrier weakened, and then, the dragonfires were the final kill.

Thus, Oblivion was opened.


Admantia may have only guarded a portion of the barrier.

Many other things guard the barrier. Oblivion did open.

It is obvious, whatever the mythic dawn needed to do and mess with, that they did and messed with.

Otherwise, the crises would have never taken place.

Actually, the most powerful force ever, Plot, dictated the crisis had to happen.

Oblivion is above us every night, the only thing that "guards" us from it is broken pact and shallow promise. Dagon (and other Daedra) are able to enter and exit Mundus quite frequently. The Oblivion Crisis was unique only in scope, which came about due to the intervention of the Dagonites and the fall of the Towers. It is not so much the Dragonfires that keep the barier (such as it is) stable, it is the presence of the Stone within the Tower. But even that is relative, if true at all - witness again the entirety of the Second Era.

The White Gold is unique in form. Its structure - the Tower surrounded by eight towers - echoes the Wheel and therefore gives it a special context above other towers (which are all unique in their own ways). The Intercept also hints at the divine nature of its Stone, created by a pact with the Lords of Misrule (or, alternatively, granted by Akatosh/Lorkhan).

Excuse the brevity, I must be off,
Ayaan-Si