[@ERode] Ok, my bad. No, I meant that there is a lot of different kind. Generally speaking, they are on the rare side. At least, fully Adult Dragons are rare, what they call Ancient Dragons. 

An ancient Dragon could mess up a village or a city for sure, but in such a world courts and the like would also have mages and measures in place to counter such obvious threats in a world such as this. 

The other planes do exist. Mostly untouched in my world as in DnD, so you still have the Elementals Planes, the Shadowfell and the Feywild. The Hells and Pits of Devils and Demons, etc.