Dragons

Land:
there is only three things that can kill a Land dwelling true Dragon in it's prime. One is another such dragon, second is one of their Sea dwelling cousins, and thirdly is a god. And that is for good reason, a true Dragon is called such because each possesses not only massive wings claws and fangs, (to say nothing of their fire-breath) but also a mind as cunning as any humanoid's and than some, however each true Dragon is covered from nose to tail tip with hard durable scales that protect them from most damage, (on average each is between fourty and sixty feet long most of which being neck and tail However they also have large bodies) as for appearance they have six limbs, four legs and two wings although rumours exist of dragons with different combinations.

Sea:
Although they bear many things in common with their land dwelling counterparts, sea dragons have lost their wings and have sprouted fins along the lengths of their body's, between their toes, and the backs of their limbs, in addition they have a few other differences from true land dragons, although the size and scales remain the same, sea dragons instead of fire can super heat water in their bellies until it is boiling hot and than "spit it out" in a tight stream even when underwater at either attackers or prey so be careful when battling one. In addition they have also, like the aquatic Elves, developed patterns of bioluminescent stripes unique to each dragon.

False Land Dragons:
As dangerous as true dragons are, it is certainly better for the sentient species of the isles that true dragons are relatively rare and if they do live somewhere they prefer to develop their claims not just destroy it, however, false dragons have no such qualms, although in physical appearance a false land dragon is similar to a true land dragon, false ones are not only smaller (rarely reaching above fourty feet) but perhaps more importantly, are not sentient and instead having the intelligence of a particularly smart wild animal. However they do share True Dragon's ability to spew forth fire, although in each generation of false dragons an increasing number are born without that ability.

Wyverns:
It is hard to describe what a wyvern is exactly beyond "four limbed small dragon" as unlike land dragons a wyvern has only four limbs, that is two wings (which when grounded they use as forlimbs) and two rear legs, similar to bats, however unlike dragons a wyvern's body is only around the size of a horse, anroughly the size of the same animal, however the head is more akin to a snakes or crocodile's and has large fangs that it uses to inject the venom it uses instead of fire, however they also possess a long neck and tail like dragons. A final difference is of course, that wyverns are, I wouldn't exactly say commonly, but can be ridden, often times by noblemen or elite warriors.

Sea Serpents:
Like the land dragons and the sea dragons, Sea serpents fulfill the same niche that wyverns fill but beneath the waves. Resembling an oarfish but larger the average sea serpent would be between 18 and 27 feet long and between a foot and a meter in circumference, however the bigger ones can be forced into submission and ridden by aquatic dwelling species like, again, wyverns.