The only thing one can say about dragons whith any certainty is that one never knows what to expect from dragons.
Elves are, in a way, reliable in their capriciousness. Once a man manages to reconcile their eternal patience with their changable moods, he can understand elves. But is true of one dragon is almost never true of another, for dragons are not so much creatures of flesh as part of the land, a reflection of their surroundings.
A dragon residing in barren wastes may be a withered creature, small, vicious, and cunning. One who is well fed by his surrounding countryside will be grand and regal, a dweller of ruins wise and sphinxlike.
They are as large or as small as their environs will permit, from petite wyrms the size of destriers, to grand behemoths that dwarf the greatest constructions of mankind. They have four limbs, the foremost pair of which may or may not be developed into wings, a neck and tail of varying lengths, and a generally reptillian appearance. They may eat the flesh of animals or the flesh of man or no flesh at all.
Their magical prowess depends on the innate properties of the ley-lines around them, but all dragons have the power to comprehend all tongues, if nothing else. Many have some kind of weapon in their mouths, spewing acid or flame or ice.