Your mother is an animal trainer who is constantly travelling for work. The summer of your eighth birthday, she takes you on a road trip across the countryside to remote towns you've never even heard of. You have no idea what sorts of animals she trains until you sneak out of the hotel room to follow her. In a clearing within a mossy pine forest you find your mother… with a dragon (or at least she thinks so) that is larger than she is. In a flash fire, she is crushed under the dragon's foot and you are left alone in this world.
All is not lost, however, your uncle is an adventurer who hears your cries and rushes to your rescue. You both reunite in the nearby town of Evesdale and you are now thrust into an adventure. Your uncle explains to you that your mother was an adventurer before she married your father, she left your father after he declined to join her on a quest to find the 'Dragon Relics' that grant their wielders the power to become dragons. Your mother was a dragon wielder and your father was a human wielder, and she left him to seek out another human wielder. Your family history is steeped in dragons from your mother's father to your mother to you, and because of your mother's death you are the last known human wielder. You are awoken from your daze by you uncle and you set out on a new adventure to find the dragon artifacts you have inherited.
Your uncle teaches you the arts of pushing your connection with the dragon over and above the human part that has been passed down to you. He shows you different ways to slowly work both human and dragon parts of yourself together to form what is essentially a hybrid human dragon form. Your first transformation is a simple eagle.
It was a simple enough transformation, as you have become quite accustomed to having both a dragon and a human part in your life. Indeed, you have not had any difficulty in transforming at all. It was almost as if you were born knowing how to do it. Your uncle is distraught because you have forced this trait into yourself. Evidently, there are several dangers associated with this form. You keep transforming more and more, each transformation a step more dangerous and powerful in both ways than the last. The first obvious change you know of is a bright golden aura that surrounds your entire body, albeit slightly more controlled than a dragon's standard color. Your body grows more and more like a dragon's, and you quickly develop the size and speed of one as well. However, you can feel that you have not yet reached the full potential of your human part.
Your uncle's crew is shocked to see you as a golden eagle, as they have been training you specifically toward becoming a human dragon with a long life ahead of you and a large family. They cannot believe that your training is coming to an end. You do not tell them that this was not your intention all along, you simply have not thought of the consequences of becoming a human dragon just yet.
The next transformation you make is a very simple one. It is not something that should be possible in your current state, but it is still a step toward being a dragon. In this form you develop two wings, although they are still very birdlike and essentially your second set of arms, much like grizzly bears have two sets of paws. You fly here and there, exploring and learning. One day soon you see the crew stumbling through the woods behind the small cabin deep within the forest clearing. They are trying to return from a road trip, but something is amiss with their dragon form.
You land in the clearing and you see that the crew is in a very dire crisis. All of them are in the dragon portion of the form, and they have all begun to change. They seem to be in full transformation and there appears to be no stopping them. If they continue in their current form their respiratory systems will implode. You can hear the screams of your crew as you fly over their heads to join them in the clearing.