"It's...complicated. And don't ask him about it, either. He's really touchy about it." Isaac took a deep breath before explaining to the best of his abilities. "From what I've gathered, he was an angel at one point. He was an angel of song, or something to that effect. Then, when Lucifer did the whole 'creating hell' thing, he made the mistake of leaving heaven. He became, well, a demon. And not one of these little guys that these cultists are calling up, he was an archdemon.
But, he realized his mistake and tried to go back. It took hundreds of years of convincing the Big Guy to forgive his treason, and of course he was never fully re-instated. So that's why he's here: not an angel, not a demon, just something in between. His voice, his weapon, was taken from him. His sole purpose is to hunt other demons now with what powers he has left. So, yeah, he's been around a while. But he doesn't stay if he isn't needed, and he has a knack for getting himself killed. That's why he's assigned to a keeper each time he comes back. I imagine coming back every few hundred years and seeing how much the world has changed is a little jarring, you know? I was the lucky bastard picked this time."
Isaac sighed. "He'll be back. He's still very much needed. But I don't know how long it takes. Like I said, it's kind of a touchy subject with him. It's taken me years to pry this much information out of him."
He pulled up to a motel and stepped out of the car. "Well...this'll do for now, I guess."