Remnant

Remnant's condition was the result of a rather unfortunate accident. He had opted to fly across the Shifting Expanse as he had a few times before as a shortcut, and one that provided flight-friendly thermals to ride as the sun warmed the desert. What made this instance different than the others was the incoming storm that had been scheduled for that zone. Not being in the loop of the Lightning flight warning system, he was unknowingly on a trajectory of collision.
Now this would have been bad enough on its own, but another factor came into play. Someone some time ago decided to assemble an experimental device in the middle of the desert, as one does. The age of the devise itself meant that trying to figure out who's responsibility it was would be a paperwork disaster, assuming they had filed the correct papers in the first place and not just followed a wave of inspiration to its inevitable conclusion in a flurry of innovation. So who knows who put the thing there.
Anyway.
What was important about this device was that it had remained there unknown for a long time, but the very storm that was about to occur had brought about the last bouts of wind needed to uncover it from the sand. That, and this now uncovered machinery was one that was powered by lightning strikes.
Perhaps you see where this is going.
Remnant did not, however, as the flew across the swiftly darkening sky and wondered if something was going on. He only had a few moments to wonder about this and the prospect of grounding oneself in a desert and whether that was any safer than getting out of there as fast as possible. Unfortunately the answer came to him in the form of a bolt of lightning.
Remnant was suddenly the connecting point between a thundercloud and this machine which attracted lightning. This was obviously a terrible and painful place to be. Remnant promptly lost consciousness and plummeted from the sky in a smoking heap.
When Remnant awoke he was incredibly aware of two things, firstly that he was alive somehow, and that he had an empty sort of buzzing energy feeling all over. Upon inspecting himself for limbs, which he still seemed to have in full, he watched as a flicker of energy seemed to separate from his scales, leaving nothing behind.
Remnant was disappearing.
The kind of panic that demands you seek help from complete strangers just so that anyone might help you was the kind of panic Remnant felt right then. Fortunately for him, the denizens of the Lightning flight are very knowledgeable about the subject of lighting. Unfortunately, the ancient machine had been in such disrepair and so full of sand that the insides completely glassed over in the moment of the strike. There was no way to tell what this machine did, or how to undo it.
Luckily for Remnant, lightning aligned dragons only become more invested when faced with such an impossible looking problem, not less. Innovators and engineers alike broke out hypotheses and equipment to see what they could understand.
Eventually they were able to craft equipment for Remnant to wear. It wouldn't be able to stop him from disappearing completely, but it would slow the process and even allow parts of him to rematerialize. Granted, this process would be just as random as the parts of him that were disappearing, but it meant that Remnant was not doomed to become a living ghost.
Inspired by their efforts, Remnant wanted to learn all he could so that he may become an engineer himself. That way he may be able to understand what the desert machinery did to him someday, and along the way perhaps create things that could help others overcome issues and live easier lives.