Soulless Soul Dragon

"My Lord, a foreign Dov is flying near our territory. Your command?" a dragon serving under Miraak asks his master.

"Do you know who it is?"

"Durnehviir, he fought against Alduin during the battle. He does not serve the other Dragonborn however, he serves someone else... Who? I do not know."

"Hm? Looks as if my cousin wants to gift me another servant... Bring it down, dead or alive but soul intact."

With his command given, all of his dragons take wing and begin pursuing the intruder, Durnehviir responds as you'd expect, with widescale life-draining Thu'um. He was no longer a shadow of himself, with the majority of his soul no longer held in Soul Cairne, and Michael granting him full use of his powers, he was far, far stronger than before.

Compared to the other dragons attributed to ice, fire, or water, he could now be called a 'Soul Dragon', and this clearly showed when he blasted two dragons out of the air almost instantly as the battle began.

Their flesh rotted at a visible rate, their scales crumbles as their bones snapped under their own weight. They fell into the sea below, their lifeless bodies washing up on shore waiting to be resurrected once more.

"Vax! Qiilaan wah hin yun in!" (Traitor! Bow to your new master!)

"Zu'u aam nunon gein! Hin in vust ni met mok orin voth tiinu zos eruvos mein!" (I serve only one! Your master could not match him even with countless more years of planning!) Durnehviir roars back as fire and frost burn his scales, scratching away at his already fragile wings.

"Hi fen dir! Ahrk ruz hi fen aam!" (You will die! And then you will serve!)

"Hi dreh ni orin mindok vir folaas hi los!" (You do not even know how wrong you are!) Durnehviir retorts as he launches yet another shout over his shoulder, "Gesahlo qeth sil!"

Many dragons part to avoid the attack, causing it to only hit one. Their wings immediately snap under their own weight, sending them plummeting to the ground below. Despite all the cursed dragon's efforts however, he wasn't able to fight off an army of his own kin.

Durnehviir's wings get burnt up by a powerful fire breath and his quickly begins losing altitude, eventually crashing hard into the ground after locating a 'suitable' landing spot. He rolls a couple times, destroying what was left of his wings before forcing himself to his feet, ready to fight his kin on the ground if needs be.

They all circle him like vultures until one lands nearby with a lone masked man on its back. "Miraak." Durnehviir growls, easily identifying him.

"Durnehviir. How long has it been, since I was praying at your feet like a servile fool?" Miraak asks as he dismounts his dragon.

"Ahk lingrah, hi los spein fah hin ahmik." (Too long, you are late for your service.) Durnehviir states with a low rumbling chuckle.

"Funny. Is it not you prostrating yourself to me now? How pitiful, a child of Akatosh brought low by one such as I?... Do you remember? The moments where I devoured the souls of your closest kin? Forced you to flee to whatever realm of Oblivion you ended up in?"

"I do. And you will pay for not just in blood, but in spirit."

Miraak laughs, "Oh, I don't think I will! Who of your allies would face you when you turn against them!? GOL HAH DOV!" he shouts, using Bend Will to force Durnehviir into submission. He wished dearly to know who the dragon's master was, who he would need to kill for his plans to come to fruition.

Only for his shout to wash over Durnehviir with no discernable effect... Durnehviir just grins at him, rising up to his full height. "Hin sahlag togaat funt hi, Miraak!" (Your pathetic attempts fail you, Miraak!), "RII VAAZ ZOL!" he roars, using the Soul Tear shout to try and end the First Dragonborn once and for all.

It strikes true, causing Miraak's body to visibly begin to pale and age... Not for long however, as he turns to the dragon that served as his mount. "Zi Los Dii Du!" he shouts, all at one tearing its soul from its body and taking its vitality for himself, curing him of his ailment.

The other dragons don't blink an eye at this, their brainwashed states not allowing it. But Durnehviir could see the vile act for what it is, unendingly traitorous. Alduin had never used such a method, nor would he, he valued loyalty despite all his faults, but it was plain to see that Miraak held none of the scruples that the World-Eater had.

"VAXEI VALDREK!" (TRAITOROUS WRETCH!)

"Hah! And more is yet to come until I am finished! MUL QAH DIIV!" Miraak shouts and a bright golden aura explodes out from within him, enveloping him in a huge ephemeral dragon that looked not too dissimilar from the aspect of Akatosh that'd defeated Mehrunes Dagon during the Oblivion Crises.

"Gein avok..." (One above...) Durnehviir mutters as Miraak's dragon aspect bites down on his skull, killing him instantly... The Dragonborn then attempted to absorb his soul, but found no soul to take...

Unbeknownst to him, Durnehviir's contract through the Ideal Masters and now under Michael rendered his soul entirely to the new Daedric Lord. The Concepts Michael stole from Clavicus, Deals, Contracts, etc, made it impossible for Miraak to ever claim Durnehviir's soul...

To Miraak though, it just seemed like Durnehviir was some kind of incredibly powerful undead puppet... That also possessed the dragon's memories. In response to his pyrrhic victory, he begins destroying the area around him. The battle had cost him one dragon and forced him to resurrect those who'd died as well. A dire loss all things considered.