Reply To: Future books?
It can be used for possession like things and possibly true possession, but also a lot of other things, triggers, compulsions and memory alteration etc.
Think of some of the nastiest things that either a bad Deryni might do (See Katherine Kurtz) or the sort of mental manipulation that Jack Chalker might do to people.
But again, like the 21st Discipline, those authors are just writing fiction. Doesn’t really exist. And if you ever found out that it existed, you would shortly forget that it existed and realize that it could never have existed and that you’d just been joking around trying to scare people.