So we all know we defeat Durnehvir in battle, and we get his Shout so we can summon him to Tamriel temporarily.

Its interesting because Durnehvir says he seeked out the Ideal Masters so he could become more powerful then the other Dragons so he could be superior to other dragons. We know Durnehvir knows Aldion because he mentions him if you have finished the main quest. The question is was Alduin one of the dragons he was trying to become more powerful than? I think he was.

Did Durnehvir succeed in that mission? I believe he did....at a terrible cost.

Durnehvir can't die now. He also has no soul as the Dragonborn killed him, but there was no soul to absorb. He is literally an undead Dragon as the Ideal Masters own his soul...so there is no soul to absorb. Durnehvir is actually beyond death, and in some points of view has become more powerful then the World Eater....but at a heavy price being bound to the Soul Cairn and the service of the Ideal Masters who own his soul. At worst Durnehvir is equal to Alduin now, since neither can really be killed...Durnehvir will just reform in the Soul Cairn, he can't die....Alduin can be displaced and sorta die temporarily until akatosh decides its time for him to comeback....

its interesting...in Durnehvir's lust for power over other Dragons, Alduin included, he got his wish at a cost much greater then any power he could ever acheive...he is trapped in the Soul Cairn forever....and is literally the "Death Dragon"....what a horrible fate.....although Durnehvir could fight Alduin now forever and Alduin would never be able to kill him permantly like he could other dovah...Curse Never Dying...how fitting eh? You have to admit though, its crazy what Durnehvir had to give up to get that power....

I don't think Durnehviir became more powerful than Alduin. Remember, you need a certain shout to even get Alduin to be hittable.

Plus he can't consume the world, I don't think.. so..

Also I dont think Durny can consume the souls of mortals like Alduin.

Or resurrect dragons. I mean he dabbled in necromancy.. but not to that extent, I don't think.

I still think he is a much more powerful Necromancer then Alduin, His personal "Soul tear" shout and summon undead horde shout come to mind.

True but Durnehvir can't die....as far as i know, Alduin consuming the world doesn't include the Daedric Realms/The Oblivion Realms(Unless im mistaken, I doubt the Daedric Lords will just stand around and let Alduin eat them, and even if they do the Daedra survive so it would be fair to assume the Ideal Masters servents, such as Durnehvir would survive that)...Durnehvir is bound to the Soul Cairn and the Ideal Masters...he has actually become part of the Soul Cairn...so he gained equal power in his own right...just not "the same" power as Alduin....but Alduin could never kill him....atleast not permantly....they would battle multiple times with Durnehvir just reforming himself....seems like a stalemate...

This is an intresting discussion though, its why i love these forums....Durney is the only dragon that can be killed and just reforms...he don't need Alduin to bring him back to life....of course the Ideal Masters own his soul and he is enslaved to them forever...the price for his lusting for power.