|A Bone Man, probably|
Drop those sorcerous rituals that upset some people and replace them with drugs. Now you've got an acid weird western on an alien world. That ought to be enough for any game, but you're a jaded bunch with a decadent palate so don't let the alien thing keep you from borrowing from Forteana related to the America West: tombs of giants, tiny mummies, underground lizard (or snake) men. Thunderbirds. Season to taste with Shaver mystery.
Saddle up, cowboy. Lost Carcosa awaits.