Everything is a shade of Gray
"For the thing that I have greatly feared has come
upon me. And what I have dreaded has happened to me.
I am not at ease, nor am I quiet; I have no rest, for
trouble comes." Job 3:25,26
But if I wanted to be less literary about it all, I'd say that my previous campaign revolved around the question, "So tell me, what is it you want? (For that is the question which drives us)."
And perhaps a lighter, more humorous look at the overall theme might be something along the lines of "Don't trust fiends, regardless of circumstance, regardless of necessary evils, and regardless of whether they're smiling when they lie to you."