Shadowfell

Shadowfell is a nasty piece of work by all accounts. A brilliant piece of work, but no less nasty for it. Most of the time the dragons around him just pray he stays in his study, deeply absorbed in unravelling the weft and weave of the universe. Whenever something rouses him from his research, he stomps from argument to argument in a dark mood. Unfortunately, he has a tendency to settle all his arguments with equally dark magic.

Arrogant even as a hatchling, Shadow spent more time among adults than dragons his own age. He idolized his mentor especially. A powerful mage in her own right, Brightscale was renowned for her wisdom and magic. Dragons took to calling him Brightscale's shadow, and the name stuck. Over time, as Shadow's power grew, he began to chafe at this comparison. One day, he and his mentor had a tremendous quarrel. That night, there was a terrible explosion. Brightscale was destroyed, alongside her life's work. While evidence pointed to a spell gone wrong, suspicion fell on Shadow. Furious at the accusation, Shadow cursed his clan and vanished in a puff of smoke.
Shadow has spent many years thereafter wandering from clan to clan, lending his formidable power to whoever could tolerate his awful temper. In his path he left many ruined lives and cursed dragons. So it was only a matter of time before somebody took the arrogant Skydancer down a peg (or five). Confronted by another student of the late Brightscale, Shadowfell challenged the distraught dragon to a duel. In the seconds it took for him to mutter the words to a fearsome petrifying hex, his opponent had unleashed a curse to end all curses. Literally.
Since that day, try as he might, the dread Shadowfell has not been capable of so much as a fire-lighting charm. His magic has been locked away, deep inside him, his gem cracked and dull. Without the benefit of his incredible powers, no clan would take him. Bedraggled and ruined, he began to lose his mind entirely, unravelling at the roughly sewn seams of his being. In this state, he was discovered by Wick, a dragon he had cursed many years before. Captured and held against his will, it took some time for him to convince his captors that he could not undo the curse he'd laid, even if he'd wanted to. For the moment, no-dragon can agree what to do with him, and until they decide, Shadowfell remains imprisoned.