plot question: how did beating Merunes help?

[archchancellor]

Hey just curious about one of the plot mechanics... it really doesn't make sense to me.
First, let me reference the oblivion wiki:
http://www.uesp.net/wiki/Oblivion:Amulet_of_Kings

"The Amulet was given to the first Septim kings by the gods themselves, in order to light the Dragonfires and keep the Daedra of Oblivion at bay."

So amulet's power number 1 is: can light dragonfires.

also,
"Martin uses the amulet to bind himself to Akatosh, and defeats Mehrunes. Though the amulet is destroyed, so is Mehrunes himself, and Oblivion no longer poses a threat to the mortal world. "

Power number 2: can break amulet and thus bind self to Akatosh for short time before turning to stone..

From the article and the game itself, I infer that the threat of Oblivion is over BECAUSE Mehrunes was defeated. In effect, there is no invasion force without Mehrune, the guy who was leading the whole party.

Which brings me to my main question:

But... isn't he immortal, like all daedra? That means that defeating him didn't solve anything.

And the only way to shut the oblivion gateway was to light dragonfires, wasn't it? Doesn't that mean that the gates should've still been open, and that the fires would have to have been lit some other way?

And do the fires repel passage to all planes of oblivion, or just to Mehrune Dagon's?

And on the side: Why was shutting gates pointless after Dagon came in? Couldn't Martin have trapped him by lighting the fires at said point?

[AnimaMortis]

IMO
the gates have been closed because Martin lit himself. he didnt just make himself an avatar of Akatosh, he also lit the dragonfire, which still burns inside the statue, or something. So in effect, Martin became the dragonfire, which was a manifestation of Akatosh. But, since he was conscient as well, he could direct his form to a powerful one, one that could defeat and banish Mehrunes Dagon, thereby also eliminating that threat to Tamriel.

Then, which gates closed. Id say all of them. just because Mehrunes Dagon was the first and, to our limited knowledge, only Daedra lord to use Oblivion gates to invade Tamriel, doesnt mean the others couldnt. Mehrunes had the time to prepare, since he was the mastermind behind the plan to invade Tamriel. If the other Daedra lords knew about Tamriel being vulnerable to attack, they still couldnt have invaded, since theyd have to prepare. They wouldnt have the amount of sigil stones needed for such a mass invasion. Besides, its about the barrier that closes off Tamriel from Oblivion. Since there is no specific realm named, its very plausible that they mean all realms of Oblivion. With the death of hte emperor that barrier weakened and Mehrunes knew and was prepared to invade immediately after.

Then, why pointless when Mehrunes came in?
well, he IS a Daedra lord. Hes one of the mightiest beings in existence. He could destroy Tamriel on his own if he wanted to.(would take him one helluva lot of time) Thats why. And, i think he might be able to summon his own daedra, like normal, puny, mortal conjurers.
Martin could have trapped him in Tamriel, but would YOU want a real big, four armed guy, with really destructive tensions, who wants to first destroy the world, then rebuild it with mortals as slaves to the daedra, who cant be hurt, except by artifacts made by himself, and by his WHOLE name, of which only the first part is known to man, in your living area?
I think not.

[archchancellor]

So if the statue is the flame, then if someone were to tear down the statue, then oblivion could open up again? That doesn't seem right.

[Vook]

I understood it differently. The amulet, the emperor, the dragonfires were a seal of union between Alessia and Akatosh, a thin barrier between the worlds of humans and daedra maintained by Akatosh [ ref ] so that Daedra wouldn't invade but humans could tap into Daedra powers.

With summoning Akatosh the pact was voided, but humans were given a chance - instead of fragile barrier, the gates were sealed permanently. (in fact all the conjuration school of magic tricks should stop working...)
Whether Mehrunes was killed or just banished is purely academic matter. The gates can't be reopened.

Now imagine what happens if Martin just relights the dragonfires.

Ocato: run for teh temple
Dragonfires: *whooosh*
Gates: *Zzzziwh*
Martin: teh fires burn again
Dagon: whoops im trappd
Dagon: shucks
Dagon: oh hello thar martin
Martin: oh hello thar dagon
Dagon: *thud*
Martin: *splat*
Dragonfires: *poof*
Gates: *whizzzZ*
Dagon: nvm continue with invasion
Daedra: yay
Ocato: shucks

For yet another alternate ending see my post in this thread