I am trying to think of or learn about some sort of demon/spirit/supernatural creature that would carry out the darkest desire in a character's heart. My character is going to think "I really wish s/he were dead" like you do sometimes when you're angry/jealous, but he won't really mean it. So, what I need is some sort of demonic, etc. force that would read those thoughts and carry them out for him.
Is that clear? I did find a demon that incites men to murder, which I could always use in a pinch, but my character wasn't there when the murder happened, so I actually need it to be an outside force.