fact: Billy G.'s name is a reference to Michael Jackson’s 1983 song "Bille jean" that was released on the thriller album and released as a single a year later. Alongside "beat it" and the title track!
Billy G. used to sell and breed gold fish and koi (in a humane way, not a cruel way). It got to the point that he could go to any fish and play with them. Yes, literally play with a fish. And this isn't just fish, it stayed true with sharks, dolphins, and whales.
Wait, Hold up, what are your headcanons about Billy G. And necromancy???
:O have we not talked about them before?? Long post time.
OKAY ramble time. Starting with some basics;
Billy G. IDs as panromantic, asexual, and gender non-conforming! They use she/they/he and neos!
They always had an interest in magic, and were admittedly very skilled with it for a human! He was constantly looking for more knowledge on the matter, but was very cautious of it; she knew that it could be dangerous.
They don't remember how they wound up in the clan, or much of anything from before joining. She doesn't mind, however, as what could she have had before that he doesn't have now?
He was very close with Dusty and Coudface, but primarily Dusty. She was pretty young when she joined and the clan was still fairly small, with Dusty having not hit the prime of his leadership yet. He took her under his wing and they were pretty close!
As for the necromancy... Dusty's death was inevitable, with his health rapidly deteriorating. He was old, already in his late 80s, and had accepted that his death would come sooner or later. Billy wasn't ready, however. They became obsessed with finding a way to cheat death; to keep not only Dusty alive, but maybe even the entire clan. Dusty and Cloudface grew increasingly concerned as she became reckless in her desperation, but the two were able to talk her into avoiding anything too dangerous.
When Dusty died, however, Cloudface became a husk of his former self out of grief for his husband of over 60 years. So, not only did Billy have to face the death of one father-figure, they had to watch the other all but die with the first. At this point, Cloudface becomes leader out of barely more than formality, trying to keep up the golden age his husband had started. Billy acted as his right-hand (and interpreter, as Cloudface became entirely mute) but was delving further into the art of necromancy. After Cloudface retires, Billy steps up and becomes leader, opting not to take a right hand. The clan is still in grieving for their leaders, which allows Billy's spiral to go unnoticed.
Billy had done his best to preserve Dusty's body, but technology at the time wasn't good enough to outright prevent decomposition. They were growing more and more desperate, stitching new parts to replace what was rotting, but nothing they tried was bringing him back. So, they sought out their last resort; a dragon. (Yes, she suspected that Jaques was one, but they were not a fan of her and she knew such a young hatchling living among humans wouldn't be able to help her)
He found what he was looking for, on the west cost; a wild, adult dragon willing to convene with a human. He pleaded with her to help him, and she sympathized with his story; she had lost her children, two eggs destroyed and one stolen by humans. So, she gave him the spell, and its required dragon scales and bones, and he returned to the clan to bring forth T.R.N.K.
Dusty's mind was still there, yes. But he was buried under that of the dragon whose essence had been used to revive him, and fragments of those pieces Billy had used to repair his body. T.R.N.K., or so called Trunk, was in constant agony. It couldn't communicate, couldn't function, and Dusty could only do so much to keep the amalgamation intact; a month after its revival, Trunk snapped and went on a rampage, taking multiple lives and injuring countless others. Jaques took charge as Billy broke down, rallying the panicking Toppats into trapping and destroying Trunk.
Billy knew she'd fucked up big time at this point and just... left. Ran far, far way, weaving enchantments through themself to prevent them from fading away. They had bested death and seen the consequences, but she couldn't bring herself to face her own inevitable demise. He made himself functionally immortal, but the energy it took left his body to decay as his soul slowly trickled away.
Jaques would have hunted her down and killed her for what he'd done, and they knew that. In trying to cheat death once more, they instead caused their own fall.