A character: A wizard-school drop out who only ever learned one spell, who travels the country as a specific kind of healer - he casts out devils that were hiding in your body that were making you act like a dick. There's a whole show of presentation as he explains the whole process and where the devils are hiding in you - and particularly cantankerous potential clients/patients get the same diagnosis: You've got devils up your ass. That's why you're like that.
For a small fee he'll agree to cast them out of you, and if you're part of that particular clientele, the whole village is going to be there to see a whole flock of devils flying out of your ass. And now you're better. Most of the people buying the service instantly feel relieved once they see all the devils flying out, and more than one instantly apologises to whoever they insulted most recently.
Everyone knows that he's probably some kind of a charlatan, but nobody can really dispute his claims because they don't know enough about how healing magic is supposed to work. The truth is, the sense of relief is mostly just placebo, and the rest is adrenaline from the shock of seeing a whole flock of devils. Several people have used the service deliberately as a convenient way to back out of whatever fight they started while saving face and not having to admit to having been wrong - apologising for the slight, and explaining to the offended party that it's not that they were being an idiot, it was those devils making them act like that, you see.
The real truth is, it's not even a healing spell. The only spell he knows is how to create the illusion of a flock of devils manifesting out of nowhere. He'll make them shoot out of your ass if you're rude to him because he's personally just kind of a dick.