InsaneJournal

Most dragons of Nirn have the same general personality traits - ambitious, power-hungry, arrogant. They see themselves superior to mankind, and were even once worshipped as gods. There’s a lot of arrogance that comes with that. To them, power equals truth. And so, Odahviing follows whomever has the strongest Thu’um. 

Up until Odahviing’s “death” after the Dragon War, Alduin was that “person”. Alduin is the self-proclaimed “Firstborn of Akatosh”, and therefore he’s asserted his dominance over the other dragons. For a while, Paarthurnax served as his first lieutenant, but after Paarthurnax denied Alduin and began helping the humans, Alduin needed a new “right-wing” dragon to serve him. And this is where Odahviing came in.

Fast-forward to the Dragon Crisis of 4E 201, and Odahviing is resurrected by his old master. Because dragons do not die unless their soul was absorbed, and Odahviing was not killed by another dragon or a Dragonborn, he was simply “laying in wait”. His body was buried in Riften, which is where he would rise again, come Alduin’s return. 

“Onikaan ni ov. I would not trust another dovah.” - Paarthurnax

Paarthurnax, being a traitor himself, knows it’s smart to be wary of a dragon’s true motives, or their allegiance. Before Paarthurnax betrayed Alduin, Alduin had never been defeated in combat. Nobody knows why exactly Paarthurnax chose to betray Alduin in the way he did. Some claim it was Alduin’s claim to godhood that turned Paarthurnax away, and others say it was Kyne’s intervention that swayed him to another path.

Either way, Odahviing sees Paarthurnax as a tyrant and a traitor, especially since it was Paarthurnax’s teachings that eventually led to the creation of the shout “Dragonrend”, which cripples his kind and forces the idea of mortality upon them.

Dragonrend is a Shout created entirely out of hatred for dragons, and Odahviing sees it as a cheap and dirty trick. Dragons are prideful creatures by nature, and though they certainly have evil tendencies, they can recognize the merit of a fair fight between mortal and dovah. It takes courage for anybody to face against a dragon.

But a non-Dovahkiin mortal? 

That’s even more impressive, if not absolutely foolish in the eyes of a dragon.

That being said, Odahviing was faithful to Alduin up until Alduin’s death. Did he help the Dragonborn? Yes. Did he give up his loyalty to Alduin without question? Not exactly. When Odahviing brings Dovahkiin to Skuldafn, he says:

“This is far as I can take you. Krif voth ahkrin.
I will look for your return, or Alduin's.”

If Odahviing truly betrayed Alduin, I feel, he would have flown the Dovahkiin straight to the portal which lead to Sovngarde. But instead, he leaves the Dragonborn in an area of Skuldafn that’s still considerably far away from the portal. Odahviing might be questioning Alduin’s authority, yes, but he’s not going to freely give the Dragonborn a direct path into Sovngarde. The battles the Dragonborn endures from Point A to Point B is possibly a “test of power” from Odahviing.

It is only until the Dragonborn returns from Skuldafn / Sovngarde to the Throat of the World that Odahviing recognizes the Dragonborn as having a stronger “Voice” than Alduin and pledges their service to the Dragonborn. If ever there came somebody with a stronger Voice than the Dovahkiin and proved themselves to be better / stronger, perhaps Odahviing’s loyalty might lean in the other direction, but he is truly a “ride or die” type of ally. He is loyal to you until you are no more.