Dragons

Before there were gods, there were dragons. Dragons ruled Xen for untold eons before the advent of the humanoid races and in their opinion they rule it still. Upon the arrival of the gods of Xen the dragons retreated south to the continent of Gondwana where they intend to wait for the gods and their creations to destroy one another before they can re-inherit the northern lands. The first generations of dragons have lived for millions of years and they are nothing if not patient.
Humanoids typically stereotype dragons to be vain, greedy hoarders with a malicious intelligence. Dragons characterize humanoids as the same, minus the intelligence. In truth dragons are complicated beasts. There is no organized nation of dragons, they are belligerently individualistic. Yet at the same time they have an absurdly complicated hierarchy. The tangled pecking order dragons have in place of a society is made convoluted by two important facts. 1). Dragons have a neigh-infinite amount of time to build a collection of favors and grudges none of which ever expire and B). Dragon offspring are always extremely different beings than their parent species. In this dragons are unique. Every generation of dragon is an entirely separate and lesser being than what came before, save for those at the bottom of the hierarchy.
The dragon family tree works as follows:
First Generation: The Great Eight. These are the first eight dragons, one for each of the eight elements: Water, Fire, Air, Earth, Light, Dark, Mana, and Chaos. They are difficult to interact with as on all scales they are beyond anything else on Xen. Each is millions of years in age and large enough that a small city could be built on one's back. In form they are wildly divergent. Anisopt, the dragon of air is made of millions of fluttering insects. Mokele-mbembe, the dragon of earth resembles a more-gigantic-than-usual sauropod. These dragons keep to themselves, and have grown so still and silent they have nearly merged with the scenery that surrounds them. Once every thousand years though, they rise and meet each other in a millennial summit. No one knows what gets discussed in these summits, as the language spoken during them is only known to the eight.
Second Generation: The Elder Dragons. These dragons you can at least have a conversation with. They are the dragons who oversee and steer the rest of dragon-kind as far as any being can. Their primary forms are what humanoids think of when they... well, imagine dragons. Mostly they are reptilian in appearance, though some are feathered and others more amphibian. Full-sized one could easily wrap around a castle, though they can shift forms when needed. If ever one is forced to speak to a mortal they can become human for a while.
Third generation: Third generation dragons don't have a special name. Some still have a few feathers and webbed feet but largely they fill the traditional mold of scaly, pointy, winged monsters with dangerous breath. These are also the dragons infamous for collecting hoards of valuable objects. While not as transcendently powerful as their elders third generation dragons are still thousand of years old and smarter than your average human or elf. They can also still take human form and will do so for their own amusement.
Forth generation: The Dracon. These are dragons that exist on a more mortal scale. They are just smaller than a horse, live about as long as the elves, and think on a humanoid's wavelength. They are still very much dragon-shaped though and shun cities and humanoid civilization.
Fifth generation: These are animals of a roughly canine intelligence and come in a few set categories. Wyverns are fliers, front appendages stretched into wings. Drakes are four-footed, and wyrms, are sea-serpents. They can all produce young but all subsequent generations just replicate what came before.
A special category worth mentioning is the Dragonborn. These are born from the union of one humanoid and one dragon, either from a second or third generation dragon. Dragonborn have a humanoid shape but scaly skin, clawed fingers and toes, and a sharp-toothed dragonian head. Dragonborn are the most rare of the humanoid races as they don't have a homeland of their own are are highly sought after as soldiers.

The original eight dragons These are the most ancient beasts in all of Xen. They were not so much fire-breathing lizards as they were primal gods. Each was the master of one of the eight elements, Earth, Air, Water, Fire, Life, Death, Order and Chaos.