God help me with the horrible glitches every time I add in an image. (6 images with hellish spacing between them)

Primordial Dragons: Demigods and Sentinels
Created for the sole purpose of warding away danger from Nirn's infant races, these earliest dragons were capable of weaving together earth-bending incantations with their Thu'um, though at risk to themselves. They fought against outside forces before the wall between Mundus and Oblivion was established. They answered to no authority than Akatosh himself, causing some of them to dutifully serve their fathers will, and others to hold themselves as high as the gods.
After several of the dragons went rogue, a new variety of dragon emerged, one of which was an agent of Akatosh sent to weed out the sentinels who were no longer serving dutifully. However, this chosen agent eventually caused the extinction of primordials by either killing or banishing what remained of them, ushering in the second species of dragon, no longer as powerful.

Tiidro-Gahkaal
A powerful sentinel in ages gone by, Tiidro-Gahkaal was famed for his exploits against many Daedra and their powerful cults. He was one of the most decorated sentinels, having several intricate golden studs in his horns from grand conquests, a sign of power and status; though his name along with the others has been wiped from history.
His final stand was against Molag Bal himself upon an attempted entry into Mundus through a rift in reality, Tiidro-Gahkaal wounded the Daedric Prince enough to force him to retreat to Coldharbour, but in the process suffered a mortalizing blood curse that overtook him not long after he sealed the Oblivion rift.

Greater Dragons: Allies of the Agent
After the memory of the Primordial Dragons were erased from history, the second breed of dragon quickly took their place. Lost was the godlike powers and knowledge of reality-twisting Voices, but these dragons refined Thu'um into an art of three words and guarded it jealously. Unlike their forgotten predecessors, these dragons did not live entirely independent of any authority other than the gods, instead swearing subservience to the strongest among them, that being Alduin.
The Greater Dragons desire to conquer still lived within their souls, though they followed Alduin's lead, who led them to conquer the free races of Nirn. This rebellion eventually led Ma-Tylda to call away the Jills in an attempt to cull the numbers and power of dragonkind.

Peytagthul
One of the last dragons to be born, Peytagthul was amongst several other dragonlings who were without their mothers. Being so young with no known parentage, he slowly grew while wandering Tamriel and hunting for himself, as many of the dragonlings were forced to do with little support from their elders. Peytagthul relied on himself, but was occasionally shown kindness by mortals who he crossed paths with, leading to a lifelong love of cheese and sympathy for the mortals whose draconic masters treated them poorly.
When the war between men and dragons broke out, Peytagthul without hesitation sided with mortalkind, though he never taught Thu'um like Paarthurnax.

Lesser Dragons (or Atumeire): Cursed and Exiled
The stunted, weak and ill amongst dragons were cast out as not to weaken the fold. Often these shunned banded together to defend themselves and each other, living in social groups and migrating to separated landmasses, such as the Isles of Exile, calling themselves the Atumeire Dovs.
When Ma-Tylda called away the Jills, the Atumeire Jills managed to refuse her summons, and were in turn cursed to 'know time' for defying the gods, causing Atumeire to develop a lifespan. They eventually grew smaller in stature to their counterparts and developed thick skullplates as their horns became shorter and their bodies became more compact. These dragons attempted to wage war on the free races of Algard, but eventually drew a truce with Asgard, becoming partners and mounts to the Valkryior.

Tornirzul
A high-ranking member of the Valkryior, Tornirzul and his partner Shoanna Brunhildottir are decorated giantslayers. Being the mount of the new captain to Asgard's most powerful force has earned him much renown amongst the inhabitants of the realm. Like all dragons who serve with the Valkyries, he wears favor of his rider's feathers, which has been tradition since the first pair of Dragon and Valkyrie, Venmuldrog and Arnegael Wing-Maiden, who used the favor to signify mutual respect.