Hatchling
When a wyrmling is ready to hatch, it begins feeding on the inside of the egg’s shell, absorbing the remaining nutrients. This activity strengthens the young dragon and weakens the shell. The wyrmling then breaks free by clawing at the sides, pressing against and cracking the shell with brute strength, and blasting the shell occasionally with its own already developed breath weapon.
Wyrmling
A newly hatched dragon has a full array of abilities. Although inferior to those of a young dragon, these abilities are sufficient for the wyrmling to take care of itself, at least against relatively weak threats and predators. Although an emerging wyrmling is sodden and somewhat awkward, it can run within hours of hatching and can fly within a day or two. A wyrmling’s senses are fully acute, and—due to the interweaving of a dragon’s centers of memory and instinct—it is born with a substantial amount of its parents’ knowledge imprinted in its mind.
Even so, a dragon is not born with the full memories of prior generations. Rather, a wyrmling has a grasp of the generalities of the world and of its own identity. It knows how to move, how to use its innate abilities, who and what its parents are, and — perhaps the most important — how to view the world around it. This awareness is one reason that even the youngest dragons are capable of surviving to adulthood.
Parents might accompany a wyrmling on its earliest hunts, to protect it and to make certain it knows how to hunt efficiently. Wyrmlings left to fend for themselves and wyrmlings that don’t have protective parents still must leave the nest within a few days of hatching to find food. By the third or fourth foray, even solicitous dragon parents let wyrmlings hunt on their own, lest the wyrmlings grow too dependent on parental assistance.
Wyrmlings spend a few years dwelling with one or both of their parents. Some parents welcome this time as an opportunity to teach their offspring lessons beyond its inherited knowledge: the best areas to hunt, what to look for in a lair, and other knowledge a growing dragon needs to gain. Other parents look on wyrmlings as necessary evils: competitors for resources and for space in the lair that must nevertheless be tolerated for a brief time. Only evil dragons that lack any parenting instinct, although extremely rare, consider forcing a wyrmling to leave the nest early.
A wyrmling whose parents abandoned it before it hatched or could not care for it after it hatched takes longer to hone its abilities. It still has the advantage of its inherited instincts, but the lack of a teacher makes perfecting its abilities an arduous task. Some wyrmlings manage to do so on their own, through trial and error. Others seek out mentors of their own kind. Even an evil dragon might willingly take on a short-term apprentice if the younger dragon shows adequate respect, such as material gifts. These relationships rarely last more than a few months, because the older dragon inevitably begins to view the younger one as a rival. The younger dragon either departs or ends up on the menu.
Although wyrmlings are small and weak by dragon standards, a wyrmling is roughly the size of a large wolf or a full-grown human. Even at their youngest, dragons have few natural predators.
Young
By the time a wyrmling becomes a young dragon, it has grown to roughly the size of a horse, and its lairing and territorial instincts are stoked into a raging fire. A young dragon must leave the nest (if it has not already done so) before territoriality and greed transform the parent-child relationship into a bitter rivalry.
The relationship between a dragon and its full-grown offspring depends on the individuals in question. For the most part, dragon parents and children retain a loving relationship; though they do not share territories, they harbor affection for each other and render assistance if the other is in danger. A rare few go the opposite route, treating their parents or offspring as competitors for resources — highly dangerous competitors at that since each knows the other so well — and end up violently at odds.
The first task of a young dragon is to find a lair of its own. This task can prove challenging because the territory the dragon knows belongs to either a parent or a mentor. Thus, a young dragon must depart the region it knows best to find a spot isolated enough to serve as a lair, yet still near enough to viable hunting grounds to make foraging possible.
Young dragons use existing structures (such as abandoned castles or mines) or natural hollows (such as caves) for their lairs. Later in life, when a dragon has more power, knowledge, and confidence, it might build, or find others to build, a better home. At the young stage, though, it just needs to find something viable.
Adult
Adult dragons revel in the fact that they are among the mightiest predators in, particularly if they have had a successful youth. At this age, adult dragons seek to expand their territories dramatically or even to move their lairs, abandoning whatever haphazard sanctuary they might have found as youths in favor of larger, more comfortable, or even custom-built homes. These efforts sometimes pit them against other dragons or territorial creatures. Thus, adult dragons are the most likely to initiate combat with other wyrms.
Elder
By the time it becomes an elder, a dragon has likely found or created its permanent lair and has well and truly established its territory. Although a few elder dragons continue to expand their domains, most are content with their holdings (barring environmental changes or famine) and are more likely to be the defender against encroaching younger dragons than they are to initiate such conflicts.
Elder dragons have lived long enough that they have fully adopted the long view in terms of their goals and efforts. Unless they are acting in immediate defense of their territory or offspring, there is hardly ever a reason to hurry, and it is better to do something right then to rush. To fill the time between, they will entertain their minds with puzzles, whether benign pursuits or malicious scheming as well as the accumulation of knowledge and magical treasures.
Ancient
By the time it becomes ancient, a dragon ranks among the most powerful creatures to walk the earth. Its lair is nigh impregnable. Its name (or at least one of them) is known far and wide among dragons and humanoids both. The dragon has survived longer than most nations.
The truth is, the dragon doesn’t have much left to do. The dragon’s territory is as large as the dragon wants it to be. If the dragon wants to manipulate and control the nearby communities, it does so. Few rivals exist with sufficient power to offer the dragon anything resembling sport. For an ancient dragon, perhaps the greatest challenge is staving off boredom.
Some ancients spend years hibernating for lack of anything better to do. Others ignite conflict, invading other dragons' territories or inspiring humanoid allies to go to war, in hopes of finding a challenge to pass the time. A few revert to behaviors of younger dragons, hunting and raiding at whim. Some devote themselves fanatically to whatever religious beliefs they hold, or seek out new ones.
Twilight
Even dragons eventually succumb to the ravages of age. As death approaches, the wyrm enters a state dubbed as "the twilight." Although the average age of a twilight dragon is within a couple of decades of maximum age, some dragons enter the twilight more than a century earlier. Others enter twilight only in the last few years of life. Some never enter twilight, going overnight from full, ancient health to death of old age.
Twilight is the only time during a dragon's life span when the creature grows weaker rather than stronger. Precisely how this weakening develops differs from dragon to dragon and appears to have no correlation with the dragon's variety.
Death
The mighty dragons, despite all their power, are still mortal. With the exception of those who extend their existence by unnatural means, death eventually comes to them all. Most dragons die in battle — defending their territory from rivals, invading other wyrms' territories, or falling victim to the business ends of humanoid adventuring parties' swords and spells.
Those who reach the end of old age find themselves in a quandary. Although some dragon varieties can will themselves to die, others do not have that capability. Thus, those powerful or lucky enough to reach old age face the slow decline into twilight, further weakening, and, eventually, death.