I don't think I will push Satan's evil doing that much, but I think that no matter what, somebody will complain about my theme.
Perhaps, but that theme is very much in vogue right now, what with the Left Behind books and the newest release of Risk (Godstorm). I think most people will see the fantasy element in your theme and be okay with it, regardless of their actual beliefs.
Remember when D&D was called satanic by some major Christian programs and ministers? My friend vividly remembers a 700 Club program dedicated to the topic. Some people were convinced that Player's Handbook actually taught people how to cast spells.