Dragons

Widely regarded as the apex predator of the natural world, dragons are unrivaled in their raw strength, cunning, and magical connectivity. Despite their usual depiction of aggressive brutes, dragons are inherently intelligent beings with a potent connection to The Magical Weave (indeed, without this innate magic, they likely would not be able to physically fly or use their breath weapons). 
As one of the three Primordial Titans, dragons were once the uncontested masters of the sky, but they too fell victim to The Great Diminishing and were largely relegated to the stuff of legends among mortal civilizations. Nowadays, most humanoids will go an entire lifetime without ever seeing a true dragon (far more common are their cousins: wyverns and drakes) and those more privy to draconic lure believe there are likely no more than a few dozen ancient dragons across all of Archaios, and fully adult dragons likely only number within the hundreds.
Like the other Titans, dragons have been driven to such rarity simply because they cannot keep up with the vast numbers of mortal races, and while a single dragon is more than capable of razing a settlement and slaughtering scores of peasants, their are enough skilled warriors out there that can hunt them back to their lairs and slay them that dragons are forced to be very picky in where they set up shop. Because of this, dragons are fiercely territorial, even among members of their own sub-species. And since a fully grown dragon can command miles upon miles of territory, it can be prohibitively difficult for young dragons to carve out a place for themselves.
It also doesn't help that dragon mating seasons can be spaced decades apart. Granted, a dragon's clutch can contain upwards of half a dozen eggs. But even then, only one or two of those wyrmlings can be expected to make it to adulthood. 

Chromatic, Metallic, and Gem

Dragons can be broken down into three main categories, each derived from the physical appearance of their hides. Chromatic dragons boast vibrant, colorful scales and tend to be the most aggressive, territorial, and malevolent of dragonkind. After the Great Diminishing, it was the chromatic dragons who spearheaded any attempt to hang onto their old influence.
Metallic dragons have scales that resemble a wide array of precious minerals: gold, silver, bronze, etc. Metallic dragons also tend to be more hospitable of both fellow dragons and mortals alike. Some even go so far as to live amongst mortals in disguise; taking on forms that don't raise suspicion (it is a common misconception that only metallic dragons can polymorph themselves. In truth, any sufficiently powerful dragon has the ability, but most chromatic dragons are prideful and arrogant and believe that taking on a different form is beneath them).
Lastly, gem dragons are the most reclusive of the three and the most rare to be seen by mortals. They do not share their chromatic brethren's desire to reclaim their lost glory, but they also do not share their metallic brethren's interest in intermingling with the new dominant species. Instead, they are content to be left alone, and as such make their homes in the lost, remote corners of the world where they pursue their own individual growth and development and only sparingly interact with others of both their own and mortal kind when they absolutely have to.