One of the things I approved of when AD&D2e appeared was that they made dragons a lot more fearsome, giving them more (and more dangerous) attacks, more hit-points, and more scariness in general.
|AD&D 2e PHB Frontis|
But that's slightly off the topic.
A few years ago (about '03 or '04 I think) I gave some thought to how I wanted to treat dragons in my own campaign. I didn't want to stray too far from the traditional D&D tropes, but I wanted to fill out the back-story a bit, so to speak. What follows is the text of some notes I wrote to myself back then, and which I just rediscovered.
"Dragons consider themselves to be the dominant — the highest, most perfect — life form on the face of the planet. Humans (and most of the other sentient species) are of little interest to them except as occasional pawns, or snacks — though for any dragon other than a juvenile, a single human being is a fairly unsatisfying morsel.
Dragons spawn in large numbers, and abandon their young to the vagaries of fate. The mortality rate among wyrmlings is high; few will survive to reach adulthood. Those who do, however, find themselves at the top of the food chain and are unlikely to find themselves seriously challenged.
When they are first spawned, dragons are unintelligent and operate purely on instinct. That instinct revolves around eating and avoiding being eaten. Later, as they grow, their intelligence develops along with their bodies and their instincts turn to mating. Dragons will mate and spawn only a few times in their long, long lives.
After mating and spawning, the intelligence of adult dragons increases rapidly to the point of sentience. This stage of life is when they begin to gather their hoards. The motivation behind this behavious is unknown, but there appears to be elements of competition for status with other dragons. Certainly, they don't appear to have any obvious concrete use for their gathered wealth.
As dragons grow older, their mental powers increase steadily and they begin to develop powers which may be psionic in nature. Prescience, telepathy and mental domination are all traits commonly shown by elder dragons, but a wide range of other abilities have been known to manifest."
Obviously there's a lot more that could be said on the subject, and there are many questions still to be answered, but that fragment sets up some useful gaming situations. If a young dragon spawns near an inhabited area, the resulting plague of wyrmlings could pose a significant threat that would only get worse if left alone. Elder dragons might be in demand as oracles, with their powers of prescience — but the price is bound to be steep, and there's always the danger that the supplicant might become a snack.
I've yet to think about things like how much a dragon needs to eat... maybe the need for food is something that diminishes as their other powers grow? That would explain how such huge carnivores can afford to live in isolated, relatively barren locations like mountain caves? I'm not one to be too anal about things like food chains and the like, but I do like to have some explanation for why they might be out of whack.