Kaimu

Well... if you deal with dark powers beyond mortal ken for long enough, it shouldn't be TOO surprising when shit happens, now should it?

Meet Kaimu. She got her start in the dark ages, as a witch. Mind you, back at the beginning of that, witches were simply wise women, not anything to fear. Then those damned monks published that book, and it all went to hell. In Kaimu's case, this was... well, rather more literal.

She'd never held with the idea of hell, though. She thought of it as just another place, albeit a rather unpleasant one, and she'd learned enough to be more than capable of dealing with the first few demons who came after her. Of course, that didn't last.

However... someone among the ranks of demons saw some promise in her. She was offered a deal... a second chance, and more power, with her soul to be forfeit should she die again. She jumped on the offer, of course, and she was sent back, waking up in her grave and clawing her way out.

From there? Well. She kept to herself, learning what she could do, and then she vanished from history. At least, after a fashion.

Her second chance came with some significant perks. For one, she had significant magical powers, making her a top-class sorceress, at least in theory. For another, she was immortal, after a fashion. She could DIE, but only if she was killed by someone. Otherwise, she did not age, and this proved to be a significant advantage. As well, she learned to read and speak several different languages, which only helped her more.

She spent hundreds of years moving from place to place. Staying five or ten years, before moving on, she became something of a legend, though that legend has been lost to time(thanks, no doubt, to the burning of a few texts). And, well... by the present day, she's been changed further.

No human could live forever. Our minds aren't set up that way, plain and simple. However, when she started to crack, Kaimu drew on her powers, pulling them into herself and trying to bolster her weakening will. And, well, the end result was a bit of a transformation. She's become a lesser demoness of some sort, and, as it happens, subject to many of Hell's rules. Such as, for example, assignment to a greater demon as her liege, and utter obedience.

By this time, though, Hell has been changed by earth as much as earth has been changed by Hell. Her lord amounts to some sort of infernal CEO, running a mock corporation in charge of certain natural disasters. And Kaimu? When she's not allowed to roam freely, she's relegated to the position of Office Bitch. Everyone's office bitch, snack, and playtoy, even.

As a result? Well, she's a bit petty and spiteful, particularly with micros, but at the same time she's still human enough that she's not going to do anything unspeakably nasty anytime soon. It might be that someone careful could bring out another side of her...

As far as setting, you can play with her on any point in her timeline, from when she was human to the present day, to a theoretical Scifi future.

.... yeah, wrote this up on a whim, likely to scrap it.