I was watching this contest from the very begging but waited until now for submitting my entry. My concept is based on Blackletters. Nothing speak more of the devil than Blackletters do. But Modern Blackletters, not the old classical ones. I hope you like it as I much as I do. And please fell free to ask any change you want on it. I just hope not being copied by other designers.
I have chosen to use a Pentacle. The Five Pointed Star represent energy, fluid, breath, matter and mind. And the Circle around it represent a shield of protection. It has a lot of history behind it. The Pythagoreans held the pentacle sacred to Hygeia, the Goddess of healing, whose name (HGIEiA) was an anagram for the elements water, earth, spirit, fire and air. It also have a strong association to Satan and the devil when the star is pointing downward, as we used it on the logo.