Appropriate for a halloween party?

I'd see no problem with that.... although there will be a few who won't take it seriously and see it as a joke. It depends who you invite. If it is a circle of your closest friends, you should be fine, but if its a general group of accomplices and work buddies, you may have a harder time explaining your religious beliefs, and the significance of them, to them. I'm a non practicing Occultist, but for my Halloween party I will be bringing out my William Fuld Ouija board, although it will only be about 10 of my closest friends.