I know I've said it before, but I love the Krampus. Most of my ideas came from Spectrum Games Macbre Tales free holiday supplement The Shadow of Krampus. If you want to see another version for similar style games (rules wise at least), check out this post at The Other Side. My version of the Krampus is intended to be used with Lamentations of the Flame Princess. I didn't want to like the game, I'll admit it, but I find myself more and more interested (I'll address that in a future post). Since LotFP uses a dark version of Earth as its primary setting, the Krampus seems like a great fit. A child snatching demon seems the perfect way to celebrate Christmas LotFP style.
In an interesting twist, you could have the Krampus being the good guy. Perhaps Santa's punishments for those on the naughty list are truly horrific (like a twisted Willy Wonka) and the Krampus punishes children to get them to repent before Saint Nick comes for them. You're players won't expect it.
Move 120' [walk]
Attacks: 1d4/1d4 or 1 (2 claws or birch switch)
Special Abilities: Dark Seduction (once a round the Krampus may affect one female present as if he cast a Charm Person spell, the woman may make a saving throw to resist the effect)