So, here's the thing. I'm just starting to get into the crux of my short story, and I'm fairly certain that once it's done I'm going to take my main character and start a novel (maybe even a series).
But what the main character is capable of, leaves me without an idea for a villain.
My character has the ability to control demons (particularly the 72 goetic demons of the lesser keys of solomon). He can do this with no strings attached, no moral ramifications and no temptations or his soul going to hell for doing so. He has been gifted/earned the rings of Solomon, and his seat of power is The Solomon, not just because of his adept power, but his mental prowess in understanding things.
But, he's already dealing with dark entities (I'm not looking to turn this into a heaven versus hell situation, I have a completely different series I have planned for that), so what could make a good villain for someone who already deals with (and bitchslaps) evil creatures everyday? Any thoughts would be great.
Sorry if these have already been suggested, but...
For your guy, I like a well-intentioned 'good' character for a villain (or as I prefer, antagonist. They don't always have to be evil.). Evil creatures are not a problem. People with "light" in their souls are obsessive, unpredictable, and powered by beings your hero doesn't necessarily understand.
Suggestions:
* a priest obsessed with saving your hero's soul by stopping him at every turn. This guy could be no more "powerful" than your hero, just more obsessive, and better connected.
* a woman who was terribly wronged by a demon and who sees no difference between them and their summoners. If she doesn't understand your hero's benefit to humanity, she would likely just see him as another witch trying to undermine good people.
* the person or being charged with slowing the flow of demons into this world. They might be seeking a way to cut him off from his power source, or turn the demons against him. Maybe he's related to Charon, and has seen what sort of things demons can do when a mere mortal attempts to control them.
If you insist on having an evil antagonist, I suggest someone with your hero's same abilities, or comparable ones, who
abuses the demons. Are your demons necessarily evil? Misunderstood? Not knowing much about the mythos you mentioned, it would be interesting to cause your readers to feel sympathy for the demons - as if your hero knows to respect them, but your villain summons, abuses and disrespects them.