Jackal was a cold and antisocial dragon, only ever coming into contact with others if he was in dire need. He was not particularly well known by many clans, but those that did know him, knew to fear him.
Once, he was a young scholar, full of curiosity of the world and everything in it. There was also a time he had a mate, and a clan to call home. Jackal spent years studying everything and anything that caught his interest. Then one day, much like the god of the Arcane Flight, remnants of what we know as The Shade drew his attention. Jackal spared no expense, not even his own life, to get closer to this strange and deadly power. He had to know more.
The Shade consumed him, overtaking any part of Jackal's soul that was tied to anything but The Shade itself. Jackal lost consciousness, and was sent on a violent spree that cost the lives of all his clansmen and kin. When he awoke, Jackal had forgotten his clan. He forgot his studies, his mate, and his children. The only thing he knew was his 'master', and he devoted his life from then on to serving its commands.
That eventually led to the need for a special, unnatural substance, and news of Melkor and Rose's talents had reached his ears. If anyone were capable of delivering what he asked for, it would be them. Despite initial hesitation and voiced concerns from Rose, both she and Melkor agreed to take on the task. Jackal never agreed to share exactly why he needed this toxin, but his intimidating stature was enough to convince Melkor to comply with Jackal's wishes.
Unfortunately for Rose and Melkor, the suppliment apparently didn't live up to its intended purpose, and ended up horribly disfiguring Jackal when he tried using it in some sort of summoning ritual. As if failure wasn't infuriating enough, Melkor, out of curiosity, had followed Jackal and witnessed the entire ritual. In a fit of rage, Jackal set is sights on destroying Rose and Melkor, and anyone they knew.
Jackal wasn't daft enough to attack an entire clan on his own, oh no. He had... reinforcements. There were many rumors, but the most notable thing among Vesperia's members was that remnants of The Shade had come to Jackal's aid during the attack. After forcing all of Vesperia to flee from their home, Jackal passed out from exhaustion. When he awoke, he vowed to find Vesperia and wipe them out. They knew too much.
Jackal roamed Sornieth for fifteen years searching, never finding a trace of where Vesperia had gone, and spending a few years lost in The Abiding Boneyard. He had slipped further and further into insanity as The Shade's hold on him grew ever stronger. In a last desperate attempt for The Shade to gain power, it led Jackal to find and kill six imperial dragons, as well as sacrifice himself, to become and Emperor. With its new found and powerful husk, The Shade carved a path from the Scarred Wasteland and along the coast of the Windswept Plateau where it bordered the Sea of a Thousand Currents.
After wiping out countless clans and much of what lived in those territories, Vesperia and its allies engaged in battle, overcoming The Shade's Emperor husk and banishing it from Sornieth. Nothing remains of Jackal.