Right, so on to the character herself!
For this challenge, I'd like to take on the subject of demons...but perhaps with a bit of a twist. All armies need an R&D department, even an army of darkness. So I'd like to introduce you to my Librarian Demoness, Ezri - succubus book-keeper, corrupted loremaster, and hellion researcher.
Our little hell-spawn here began her life centuries ago as a devoted scholar of lore for the Light, but perhaps got a bit side-tracked somewhere along the way. It is said that those who spend their days in an endless quest for knowledge will inevitably uncover secrets. Delve too deeply into those forbidden secrets, you might find yourself faced with the Dark. And those few who study the Dark for too long... are doomed to become a part of it, corrupted eternally by the journey into the void.
Ezri was totally, definitely, for sure only trying to look up a decent spell to cure insomnia...who knew it would end in demonic corruption?! Of course, the following centuries as a literary succubi may have turned her into a bit of a perv, but she's still a dedicated (if a bit eccentric) researcher. Trust her, she only reads those dirty books for the articles...
I'm not 100% sure on style, but my personal preference will always swing more towards stylization. Guess I'll figure that out as we go.