How to say this in Japanese?

Question:

I need to translate this for an event....

Must wear a costume. (come dressed up)
It's a potluck.
No holy objects allowed.
18 yrs & older only.


I know it sounds weird, so please feel free to ask questions >___<

Answer:

>Must wear a costume. (come dressed up)
What kind of costume is that?

>It's a potluck.
Is that a party people bring foods?

>No holy objects allowed.
What are holy objects here?