I don't mind the deal with the devil as a recon tool. It makes more sense for a mystical being to be able to do that type of stuff than someone punching holes in reality (did that make sense to even one person?), but if you're going to do that then there's a few rules:
1. if it's a straight up deal then the character must be evil or prone to self destruction
2. if heroic then the character must either not know he/she is dealing with the devil or must sacrifice only themselves in the arrangement
3. the devil will never straight out explain the deal in simple terms, there will be trickery and the outcome will NEVER be beneficial in any way to the character and should ultimately lead to them choosing to self destruct (suicide, murder)