Hell to Pay (character idea)
Here's one for you Players that want to be in debt to a malevolent being (warlock class recommended). The player (or on of the player's parents) made a deal with a malevolent being, & now it's time to pay the deal. The player gets blind sided by this & is able to beg/trick their way into letting the malevolent being to not only give them more time, but also give them a bit of their magical power. It's now a race against the clock to not pay their passed on debt.