I'm pretty sure I've heard an NPC say (blah blah) "...διάβολε" (devil). Today it would be used to curse similarly to "damn/damn it" (on it's own) but my problem is I don't think there were christians around at that time so it's probably wrong.

EDIT:
I also heard "Δόξα σοι ο Θεός ημών, δόξα σοι" which is not modern greek BUT it's used (as is) by orthodox christians in Greece (I don't know if other religions say this).
Now, I only know modern Greek but I would translate it as praise/thank our God. (singular)
Did you copy a bible or sth? XD