Might as well put up mine, since kongming just gave tentative approval to my backstory and concept:
First things first, since I haven't finalized a name for this character, I'll be using Stormbringer as a placeholder name.
Now, dragons in the Iron Kingdoms are known far and wide as beings of both great power and terrible evil. Lesser-known, however, is the fact that the source of both a dragon's power and its evil is embedded in its very heart: A fist-sized gemstone that corrupts all who touch it, a pure, undiluted shard of the dragonfather Tohruk's power, alternately known as a Lifestone, a Heartstone, or an Athanc. If left within a dragon's corpse, the dragon will eventually revive. If taken from it, the Lifestone eventually hatches a baby dragon forth into the world. Either way, the dragon survives in some form, ageless and immortal.
Stormbringer hatched from one such Lifestone, lost in the wilderness after those who slew the dragon it once belonged to ran into something they couldn't handle. In her early years, she reveled in her power, stalking the wilds and attacking travelers on lonely roads, but eventually she, too, ran into someone or something beyond her ability to handle, and was quickly incapacitated. The Lifestone was ripped from her heart and she was left to die, and though she managed to survive, the assault was traumatic enough that she's repressed many of her memories of the event, including the identity of her attacker.
After the attack, Stormbringer went into hiding deep under the earth to recover. Without her Athanc, said recovery has been slow, to the point that it's taken a century just to reach the level of power she enjoyed as a child, but without her Athanc the recovery has also been an unusual one, her powers and personality developing in new and unexpected directions without Tohruk's corruptive influence blighting her soul. Freed of the ravening hunger that takes other dragons, she has gained a sense of clarity that few dragons ever achieve and a sense of morality that none have ever achieved before, and she has come to believe these newfound traits to be worth the loss of the might a dragon of her age would have had.
Having once again reached the levels of power she used to possess, however, Stormbringer has now become curious about the world she's hidden away from. Just what is happening, out there among the mortal races of the world? She's watched adventurers from afar, every now and then, but the idea that there are whole cities of them all gathered together, trading good, raising children, living out their lives in such close proximity... The idea intrigues her, and she wants to see such things for herself.
Of course, it doesn't hurt that among the new powers she's developed is the ability to take on a variety of mortal forms, or that walking unseen among the mortal races will allow her to avoid the predations of her draconic kin, all of whom generally stay away from civilization. And naturally, blending in with the crowd in a populated area, she's also much less likely to run into whatever powerful foe it was that forced her underground in the first place...
I still need a name, of course, but I've got some ideas on that. ^^