Dragons are a species of gigantic reptilian creatures possessed of immense physical and magical strength, though they often choose to assume comparatively weak human forms through the use of a Dragonstone to conserve energy. They are incredibly long-lived, with lifespans often reaching thousands of years old, and slow-aging; a dragon 'child' hundreds of years old is a common sight.
Dragons frequently appear in Fire Emblem games.
Fire Dragons, as their name suggests, are aligned with the element of fire. Great wing-shaped flames erupt from their back, and sharp horns stand out in a frill from the back of their heads. In human form, they have crimson hair and eyes, matching their pupil-less red eyes and reddish-orange scale coloration in dragon form.
Though many seem to appear in FE6, these were in fact non-sentient War Dragons, and so are not representative of the species' intellectual capabilities, and the true Fire Dragons that appeared in FE7 did not even attempt to speak to humans before attacking. This leaves Jahn as the only Fire Dragon willing to explain anything about his species to humans, and thus all information about Fire Dragon psychology comes from him.
According to Jahn, Fire Dragons were completely rational and emotionless, in sharp contrast to humans; Jahn claimed not to even feel anger or a desire for vengeance humans for the near-eradication of his species from the continent of Elibe, though he did wish to win the genocidal struggle once and for all by using War Dragons to eliminate the humans in return. The extent to which this was actually true, given Jahn's actions during his brief conversation with Roy, is debatable.
Ice Dragons are aligned with the element of ice. They have no wings, but possess fins instead, suggesting they may have some skill at swimming. Six gossamer fins jut back from their heads, and their tails end in another large, paddle-like fin. In human form, they have light green hair and crimson eyes, matching their pupil-less red eyes and green scale coloration in dragon form.
According to the legends of Ilia, they were pacifists, ultimately choosing to flee Ilia rather than battle humans in the Scouring; one in particular, Aenir, helped the humans of Ilia survive the land's harsh climate and inhospitable snowy landscape, and was revered by Ilians even a thousand years after her death in the Scouring. (She in fact went so far as to marry a human and have a daughter and son by him, but that part seems to have not made it into the legends.)
The least is known about the Divine Dragons, though they were the most powerful of the dragon species. In human form, they tend to have purple hair, though the shade varies.
Regarding their psychology, little is known, though both Fa and Idoun (after she began to regain her soul) made it abundantly clear that, whatever the truth about Fire Dragons, Divine Dragons do not lack emotion.