The Shriveling Fire is a complex spells made out of fifteen different curses in five different languages. It immolates demons unlucky enough to get hit by it.
It can only be used on a demon who directly disobeys an order, and magicians tend to only use it when they must, seeing as it destroys a servant and leaves them exhausted. It is not used in any of the books, although it is mentioned in all four.
In times before Zarbustibal, the Shrivelling Fire was called the Dismal Flame.